Merge

dbms/include/DB/AggregateFunctions/AggregateFunctionArray.h

@@ -24,17 +24,17 @@ private:
 public:
 	AggregateFunctionArray(AggregateFunctionPtr nested_) : nested_func_owner(nested_), nested_func(nested_func_owner.get()) {}
 
-	String getName() const
+	String getName() const override
 	{
 		return nested_func->getName() + "Array";
 	}
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return nested_func->getReturnType();
 	}
 
-	void setArguments(const DataTypes & arguments)
+	void setArguments(const DataTypes & arguments) override
 	{
 		num_agruments = arguments.size();
 
@@ -49,37 +49,37 @@ public:
 		nested_func->setArguments(nested_arguments);
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		nested_func->setParameters(params);
 	}
 
-	void create(AggregateDataPtr place) const
+	void create(AggregateDataPtr place) const override
 	{
 		nested_func->create(place);
 	}
 
-	void destroy(AggregateDataPtr place) const noexcept
+	void destroy(AggregateDataPtr place) const noexcept override
 	{
 		nested_func->destroy(place);
 	}
 
-	bool hasTrivialDestructor() const
+	bool hasTrivialDestructor() const override
 	{
 		return nested_func->hasTrivialDestructor();
 	}
 
-	size_t sizeOfData() const
+	size_t sizeOfData() const override
 	{
 		return nested_func->sizeOfData();
 	}
 
-	size_t alignOfData() const
+	size_t alignOfData() const override
 	{
 		return nested_func->alignOfData();
 	}
 
-	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const
+	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override
 	{
 		const IColumn * nested[num_agruments];
 
@@ -96,22 +96,22 @@ public:
 			nested_func->add(place, nested, i);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		nested_func->merge(place, rhs);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		nested_func->serialize(place, buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		nested_func->deserializeMerge(place, buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		nested_func->insertResultInto(place, to);
 	}

dbms/include/DB/AggregateFunctions/AggregateFunctionAvg.h

@@ -27,9 +27,9 @@ template <typename T>
 class AggregateFunctionAvg final : public IUnaryAggregateFunction<AggregateFunctionAvgData<typename NearestFieldType<T>::Type>, AggregateFunctionAvg<T> >
 {
 public:
-	String getName() const { return "avg"; }
+	String getName() const override { return "avg"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeFloat64;
 	}
@@ -42,25 +42,25 @@ public:
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		this->data(place).sum += static_cast<const ColumnVector<T> &>(column).getData()[row_num];
 		++this->data(place).count;
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).sum += this->data(rhs).sum;
 		this->data(place).count += this->data(rhs).count;
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		writeBinary(this->data(place).sum, buf);
 		writeVarUInt(this->data(place).count, buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		typename NearestFieldType<T>::Type tmp_sum = 0;
 		UInt64 tmp_count = 0;
@@ -70,7 +70,7 @@ public:
 		this->data(place).count += tmp_count;
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		static_cast<ColumnFloat64 &>(to).getData().push_back(
 			static_cast<Float64>(this->data(place).sum) / this->data(place).count);

dbms/include/DB/AggregateFunctions/AggregateFunctionCount.h

@@ -23,37 +23,37 @@ struct AggregateFunctionCountData
 class AggregateFunctionCount final : public INullaryAggregateFunction<AggregateFunctionCountData, AggregateFunctionCount>
 {
 public:
-	String getName() const { return "count"; }
+	String getName() const override { return "count"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeUInt64;
 	}
 
 
-	void addZero(AggregateDataPtr place) const
+	void addImpl(AggregateDataPtr place) const
 	{
 		++data(place).count;
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		data(place).count += data(rhs).count;
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		writeVarUInt(data(place).count, buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		UInt64 tmp;
 		readVarUInt(tmp, buf);
 		data(place).count += tmp;
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		static_cast<ColumnUInt64 &>(to).getData().push_back(data(place).count);
 	}

dbms/include/DB/AggregateFunctions/AggregateFunctionGroupArray.h

@@ -4,6 +4,10 @@
 #include <DB/IO/ReadHelpers.h>
 
 #include <DB/DataTypes/DataTypeArray.h>
+#include <DB/DataTypes/DataTypesNumberFixed.h>
+
+#include <DB/Columns/ColumnVector.h>
+#include <DB/Columns/ColumnArray.h>
 
 #include <DB/AggregateFunctions/IUnaryAggregateFunction.h>
 
@@ -13,22 +17,102 @@
 namespace DB
 {
 
-struct AggregateFunctionGroupArrayData
+
+/// Частный случай - реализация для числовых типов.
+template <typename T>
+struct AggregateFunctionGroupArrayDataNumeric
+{
+	/// Сразу будет выделена память на несколько элементов так, чтобы состояние занимало 64 байта.
+	static constexpr size_t bytes_in_arena = 64 - sizeof(PODArray<T>);
+
+	using Array = PODArray<T, bytes_in_arena / sizeof(T), AllocatorWithStackMemory<Allocator<false>, bytes_in_arena>>;
+	Array value;
+};
+
+
+/// Общий случай (неэффективно). NOTE Можно ещё реализовать частный случай для строк.
+struct AggregateFunctionGroupArrayDataGeneric
 {
 	Array value;	/// TODO Добавить MemoryTracker
 };
 
 
-/// Складывает все значения в массив. Реализовано неэффективно.
-class AggregateFunctionGroupArray final : public IUnaryAggregateFunction<AggregateFunctionGroupArrayData, AggregateFunctionGroupArray>
+template <typename T>
+class AggregateFunctionGroupArrayNumeric final
+	: public IUnaryAggregateFunction<AggregateFunctionGroupArrayDataNumeric<T>, AggregateFunctionGroupArrayNumeric<T>>
+{
+public:
+	String getName() const override { return "groupArray"; }
+
+	DataTypePtr getReturnType() const override
+	{
+		return new DataTypeArray(new typename DataTypeFromFieldType<T>::Type);
+	}
+
+	void setArgument(const DataTypePtr & argument)
+	{
+	}
+
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	{
+		this->data(place).value.push_back(static_cast<const ColumnVector<T> &>(column).getData()[row_num]);
+	}
+
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
+	{
+		this->data(place).value.insert(this->data(rhs).value.begin(), this->data(rhs).value.end());
+	}
+
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
+	{
+		const auto & value = this->data(place).value;
+		size_t size = value.size();
+		writeVarUInt(size, buf);
+		buf.write(reinterpret_cast<const char *>(&value[0]), size * sizeof(value[0]));
+	}
+
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
+	{
+		size_t size = 0;
+		readVarUInt(size, buf);
+
+		if (size > AGGREGATE_FUNCTION_GROUP_ARRAY_MAX_ARRAY_SIZE)
+			throw Exception("Too large array size", ErrorCodes::TOO_LARGE_ARRAY_SIZE);
+
+		auto & value = this->data(place).value;
+
+		size_t old_size = value.size();
+		value.resize(old_size + size);
+		buf.read(reinterpret_cast<char *>(&value[old_size]), size * sizeof(value[0]));
+	}
+
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
+	{
+		const auto & value = this->data(place).value;
+		size_t size = value.size();
+
+		ColumnArray & arr_to = static_cast<ColumnArray &>(to);
+		ColumnArray::Offsets_t & offsets_to = arr_to.getOffsets();
+
+		offsets_to.push_back((offsets_to.size() == 0 ? 0 : offsets_to.back()) + size);
+
+		typename ColumnVector<T>::Container_t & data_to = static_cast<ColumnVector<T> &>(arr_to.getData()).getData();
+		data_to.insert(this->data(place).value.begin(), this->data(place).value.end());
+	}
+};
+
+
+/// Складывает все значения в массив, общий случай. Реализовано неэффективно.
+class AggregateFunctionGroupArrayGeneric final
+	: public IUnaryAggregateFunction<AggregateFunctionGroupArrayDataGeneric, AggregateFunctionGroupArrayGeneric>
 {
 private:
 	DataTypePtr type;
 
 public:
-	String getName() const { return "groupArray"; }
+	String getName() const override { return "groupArray"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeArray(type);
 	}
@@ -39,18 +123,18 @@ public:
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		data(place).value.push_back(Array::value_type());
 		column.get(row_num, data(place).value.back());
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		data(place).value.insert(data(place).value.end(), data(rhs).value.begin(), data(rhs).value.end());
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		const Array & value = data(place).value;
 		size_t size = value.size();
@@ -59,7 +143,7 @@ public:
 			type->serializeBinary(value[i], buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		size_t size = 0;
 		readVarUInt(size, buf);
@@ -75,7 +159,7 @@ public:
 			type->deserializeBinary(value[old_size + i], buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		to.insert(data(place).value);
 	}

dbms/include/DB/AggregateFunctions/AggregateFunctionGroupUniqArray.h

@@ -42,9 +42,9 @@ private:
 	typedef AggregateFunctionGroupUniqArrayData<T> State;
 
 public:
-	String getName() const { return "groupUniqArray"; }
+	String getName() const override { return "groupUniqArray"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeArray(new typename DataTypeFromFieldType<T>::Type);
 	}
@@ -54,17 +54,17 @@ public:
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		this->data(place).value.insert(static_cast<const ColumnVector<T> &>(column).getData()[row_num]);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).value.merge(this->data(rhs).value);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		const typename State::Set & set = this->data(place).value;
 		size_t size = set.size();
@@ -73,12 +73,12 @@ public:
 			writeIntBinary(*it, buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		this->data(place).value.readAndMerge(buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		ColumnArray & arr_to = static_cast<ColumnArray &>(to);
 		ColumnArray::Offsets_t & offsets_to = arr_to.getOffsets();
@@ -106,7 +106,7 @@ template <typename T>
 class AggregateFunctionGroupUniqArrays final : public AggregateFunctionGroupUniqArray<T>
 {
 public:
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		const ColumnArray & arr = static_cast<const ColumnArray &>(column);
 		const ColumnArray::Offsets_t & offsets = arr.getOffsets();

dbms/include/DB/AggregateFunctions/AggregateFunctionIf.h

@@ -23,17 +23,17 @@ private:
 public:
 	AggregateFunctionIf(AggregateFunctionPtr nested_) : nested_func_owner(nested_), nested_func(nested_func_owner.get()) {}
 
-	String getName() const
+	String getName() const override
 	{
 		return nested_func->getName() + "If";
 	}
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return nested_func->getReturnType();
 	}
 
-	void setArguments(const DataTypes & arguments)
+	void setArguments(const DataTypes & arguments) override
 	{
 		num_agruments = arguments.size();
 
@@ -47,58 +47,58 @@ public:
 		nested_func->setArguments(nested_arguments);
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		nested_func->setParameters(params);
 	}
 
-	void create(AggregateDataPtr place) const
+	void create(AggregateDataPtr place) const override
 	{
 		nested_func->create(place);
 	}
 
-	void destroy(AggregateDataPtr place) const noexcept
+	void destroy(AggregateDataPtr place) const noexcept override
 	{
 		nested_func->destroy(place);
 	}
 
-	bool hasTrivialDestructor() const
+	bool hasTrivialDestructor() const override
 	{
 		return nested_func->hasTrivialDestructor();
 	}
 
-	size_t sizeOfData() const
+	size_t sizeOfData() const override
 	{
 		return nested_func->sizeOfData();
 	}
 
-	size_t alignOfData() const
+	size_t alignOfData() const override
 	{
 		return nested_func->alignOfData();
 	}
 
-	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const
+	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override
 	{
 		if (static_cast<const ColumnUInt8 &>(*columns[num_agruments - 1]).getData()[row_num])
 			nested_func->add(place, columns, row_num);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		nested_func->merge(place, rhs);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		nested_func->serialize(place, buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		nested_func->deserializeMerge(place, buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		nested_func->insertResultInto(place, to);
 	}

dbms/include/DB/AggregateFunctions/AggregateFunctionMerge.h

@@ -24,17 +24,17 @@ private:
 public:
 	AggregateFunctionMerge(AggregateFunctionPtr nested_) : nested_func_owner(nested_), nested_func(nested_func_owner.get()) {}
 
-	String getName() const
+	String getName() const override
 	{
 		return nested_func->getName() + "Merge";
 	}
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return nested_func->getReturnType();
 	}
 
-	void setArguments(const DataTypes & arguments)
+	void setArguments(const DataTypes & arguments) override
 	{
 		if (arguments.size() != 1)
 			throw Exception("Passed " + toString(arguments.size()) + " arguments to unary aggregate function " + this->getName(),
@@ -49,57 +49,57 @@ public:
 		nested_func->setArguments(data_type->getArgumentsDataTypes());
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		nested_func->setParameters(params);
 	}
 
-	void create(AggregateDataPtr place) const
+	void create(AggregateDataPtr place) const override
 	{
 		nested_func->create(place);
 	}
 
-	void destroy(AggregateDataPtr place) const noexcept
+	void destroy(AggregateDataPtr place) const noexcept override
 	{
 		nested_func->destroy(place);
 	}
 
-	bool hasTrivialDestructor() const
+	bool hasTrivialDestructor() const override
 	{
 		return nested_func->hasTrivialDestructor();
 	}
 
-	size_t sizeOfData() const
+	size_t sizeOfData() const override
 	{
 		return nested_func->sizeOfData();
 	}
 
-	size_t alignOfData() const
+	size_t alignOfData() const override
 	{
 		return nested_func->alignOfData();
 	}
 
-	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const
+	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override
 	{
 		nested_func->merge(place, static_cast<const ColumnAggregateFunction &>(*columns[0]).getData()[row_num]);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		nested_func->merge(place, rhs);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		nested_func->serialize(place, buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		nested_func->deserializeMerge(place, buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		nested_func->insertResultInto(place, to);
 	}

dbms/include/DB/AggregateFunctions/AggregateFunctionQuantile.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <stats/ReservoirSampler.h>
+#include <DB/AggregateFunctions/ReservoirSampler.h>
 
 #include <DB/Core/FieldVisitors.h>
 
@@ -32,7 +32,8 @@ struct AggregateFunctionQuantileData
   * Для дат и дат-с-временем returns_float следует задавать равным false.
   */
 template <typename ArgumentFieldType, bool returns_float = true>
-class AggregateFunctionQuantile final : public IUnaryAggregateFunction<AggregateFunctionQuantileData<ArgumentFieldType>, AggregateFunctionQuantile<ArgumentFieldType, returns_float> >
+class AggregateFunctionQuantile final
+	: public IUnaryAggregateFunction<AggregateFunctionQuantileData<ArgumentFieldType>, AggregateFunctionQuantile<ArgumentFieldType, returns_float> >
 {
 private:
 	using Sample = typename AggregateFunctionQuantileData<ArgumentFieldType>::Sample;
@@ -43,9 +44,9 @@ private:
 public:
 	AggregateFunctionQuantile(double level_ = 0.5) : level(level_) {}
 
-	String getName() const { return "quantile"; }
+	String getName() const override { return "quantile"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return type;
 	}
@@ -58,7 +59,7 @@ public:
 			type = argument;
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		if (params.size() != 1)
 			throw Exception("Aggregate function " + getName() + " requires exactly one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
@@ -67,29 +68,29 @@ public:
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		this->data(place).sample.insert(static_cast<const ColumnVector<ArgumentFieldType> &>(column).getData()[row_num]);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).sample.merge(this->data(rhs).sample);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).sample.write(buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		Sample tmp_sample;
 		tmp_sample.read(buf);
 		this->data(place).sample.merge(tmp_sample);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		/// Sample может отсортироваться при получении квантиля, но в этом контексте можно не считать это нарушением константности.
 		Sample & sample = const_cast<Sample &>(this->data(place).sample);
@@ -107,19 +108,20 @@ public:
   * Возвращает массив результатов.
   */
 template <typename ArgumentFieldType, bool returns_float = true>
-class AggregateFunctionQuantiles final : public IUnaryAggregateFunction<AggregateFunctionQuantileData<ArgumentFieldType>, AggregateFunctionQuantiles<ArgumentFieldType, returns_float> >
+class AggregateFunctionQuantiles final
+	: public IUnaryAggregateFunction<AggregateFunctionQuantileData<ArgumentFieldType>, AggregateFunctionQuantiles<ArgumentFieldType, returns_float> >
 {
 private:
 	using Sample = typename AggregateFunctionQuantileData<ArgumentFieldType>::Sample;
 
-	typedef std::vector<double> Levels;
+	using Levels = std::vector<double>;
 	Levels levels;
 	DataTypePtr type;
 
 public:
-	String getName() const { return "quantiles"; }
+	String getName() const override { return "quantiles"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeArray(type);
 	}
@@ -132,7 +134,7 @@ public:
 			type = argument;
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		if (params.empty())
 			throw Exception("Aggregate function " + getName() + " requires at least one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
@@ -145,29 +147,29 @@ public:
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		this->data(place).sample.insert(static_cast<const ColumnVector<ArgumentFieldType> &>(column).getData()[row_num]);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).sample.merge(this->data(rhs).sample);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).sample.write(buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		Sample tmp_sample;
 		tmp_sample.read(buf);
 		this->data(place).sample.merge(tmp_sample);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		/// Sample может отсортироваться при получении квантиля, но в этом контексте можно не считать это нарушением константности.
 		Sample & sample = const_cast<Sample &>(this->data(place).sample);

dbms/include/DB/AggregateFunctions/AggregateFunctionQuantileDeterministic.h

@@ -46,9 +46,9 @@ private:
 public:
 	AggregateFunctionQuantileDeterministic(double level_ = 0.5) : level(level_) {}
 
-	String getName() const { return "quantileDeterministic"; }
+	String getName() const override { return "quantileDeterministic"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return type;
 	}
@@ -65,7 +65,7 @@ public:
 			};
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		if (params.size() != 1)
 			throw Exception("Aggregate function " + getName() + " requires exactly one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
@@ -74,30 +74,30 @@ public:
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, const IColumn & determinator, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, const IColumn & determinator, size_t row_num) const
 	{
 		this->data(place).sample.insert(static_cast<const ColumnVector<ArgumentFieldType> &>(column).getData()[row_num],
 			determinator.get64(row_num));
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).sample.merge(this->data(rhs).sample);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).sample.write(buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		Sample tmp_sample;
 		tmp_sample.read(buf);
 		this->data(place).sample.merge(tmp_sample);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		/// Sample может отсортироваться при получении квантиля, но в этом контексте можно не считать это нарушением константности.
 		Sample & sample = const_cast<Sample &>(this->data(place).sample);
@@ -123,14 +123,14 @@ class AggregateFunctionQuantilesDeterministic final
 private:
 	using Sample = typename AggregateFunctionQuantileDeterministicData<ArgumentFieldType>::Sample;
 
-	typedef std::vector<double> Levels;
+	using Levels = std::vector<double>;
 	Levels levels;
 	DataTypePtr type;
 
 public:
-	String getName() const { return "quantilesDeterministic"; }
+	String getName() const override { return "quantilesDeterministic"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeArray(type);
 	}
@@ -147,7 +147,7 @@ public:
 			};
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		if (params.empty())
 			throw Exception("Aggregate function " + getName() + " requires at least one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
@@ -160,30 +160,30 @@ public:
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, const IColumn & determinator, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, const IColumn & determinator, size_t row_num) const
 	{
 		this->data(place).sample.insert(static_cast<const ColumnVector<ArgumentFieldType> &>(column).getData()[row_num],
 			determinator.get64(row_num));
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).sample.merge(this->data(rhs).sample);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).sample.write(buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		Sample tmp_sample;
 		tmp_sample.read(buf);
 		this->data(place).sample.merge(tmp_sample);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		/// Sample может отсортироваться при получении квантиля, но в этом контексте можно не считать это нарушением константности.
 		Sample & sample = const_cast<Sample &>(this->data(place).sample);

dbms/include/DB/AggregateFunctions/AggregateFunctionQuantileExact.h

@@ -0,0 +1,229 @@
+#pragma once
+
+#include <DB/Common/PODArray.h>
+
+#include <DB/Core/FieldVisitors.h>
+
+#include <DB/IO/WriteHelpers.h>
+#include <DB/IO/ReadHelpers.h>
+
+#include <DB/DataTypes/DataTypesNumberFixed.h>
+#include <DB/DataTypes/DataTypeArray.h>
+
+#include <DB/AggregateFunctions/IUnaryAggregateFunction.h>
+
+#include <DB/Columns/ColumnArray.h>
+
+
+namespace DB
+{
+
+
+/** В качестве состояния используется массив, в который складываются все значения.
+  * NOTE Если различных значений мало, то это не оптимально.
+  * Для 8 и 16-битных значений возможно, было бы лучше использовать lookup-таблицу.
+  */
+template <typename T>
+struct AggregateFunctionQuantileExactData
+{
+	/// Сразу будет выделена память на несколько элементов так, чтобы состояние занимало 64 байта.
+	static constexpr size_t bytes_in_arena = 64 - sizeof(PODArray<T>);
+
+	using Array = PODArray<T, bytes_in_arena / sizeof(T), AllocatorWithStackMemory<Allocator<false>, bytes_in_arena>>;
+	Array array;
+};
+
+
+/** Точно вычисляет квантиль.
+  * В качестве типа аргумента может быть только числовой тип (в том числе, дата и дата-с-временем).
+  * Тип результата совпадает с типом аргумента.
+  */
+template <typename T>
+class AggregateFunctionQuantileExact final
+	: public IUnaryAggregateFunction<AggregateFunctionQuantileExactData<T>, AggregateFunctionQuantileExact<T>>
+{
+private:
+	double level;
+	DataTypePtr type;
+
+public:
+	AggregateFunctionQuantileExact(double level_ = 0.5) : level(level_) {}
+
+	String getName() const override { return "quantileExact"; }
+
+	DataTypePtr getReturnType() const override
+	{
+		return type;
+	}
+
+	void setArgument(const DataTypePtr & argument)
+	{
+		type = argument;
+	}
+
+	void setParameters(const Array & params) override
+	{
+		if (params.size() != 1)
+			throw Exception("Aggregate function " + getName() + " requires exactly one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
+
+		level = apply_visitor(FieldVisitorConvertToNumber<Float64>(), params[0]);
+	}
+
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	{
+		this->data(place).array.push_back(static_cast<const ColumnVector<T> &>(column).getData()[row_num]);
+	}
+
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
+	{
+		this->data(place).array.insert(this->data(rhs).array.begin(), this->data(rhs).array.end());
+	}
+
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
+	{
+		const auto & array = this->data(place).array;
+
+		size_t size = array.size();
+		writeVarUInt(size, buf);
+		buf.write(reinterpret_cast<const char *>(&array[0]), size * sizeof(array[0]));
+	}
+
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
+	{
+		auto & array = this->data(place).array;
+
+		size_t size = 0;
+		readVarUInt(size, buf);
+		size_t old_size = array.size();
+		array.resize(old_size + size);
+		buf.read(reinterpret_cast<char *>(&array[old_size]), size * sizeof(array[0]));
+	}
+
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
+	{
+		/// Сортировка массива не будет считаться нарушением константности.
+		auto & array = const_cast<typename AggregateFunctionQuantileExactData<T>::Array &>(this->data(place).array);
+
+		T quantile = T();
+
+		if (!array.empty())
+		{
+			size_t n = level < 1
+				? level * array.size()
+				: (array.size() - 1);
+
+			std::nth_element(array.begin(), array.begin() + n, array.end());	/// NOTE Можно придумать алгоритм radix-select.
+
+			quantile = array[n];
+		}
+
+		static_cast<ColumnVector<T> &>(to).getData().push_back(quantile);
+	}
+};
+
+
+/** То же самое, но позволяет вычислить сразу несколько квантилей.
+  * Для этого, принимает в качестве параметров несколько уровней. Пример: quantilesExact(0.5, 0.8, 0.9, 0.95)(ConnectTiming).
+  * Возвращает массив результатов.
+  */
+template <typename T>
+class AggregateFunctionQuantilesExact final
+	: public IUnaryAggregateFunction<AggregateFunctionQuantileExactData<T>, AggregateFunctionQuantilesExact<T>>
+{
+private:
+	using Levels = std::vector<double>;
+	Levels levels;
+	DataTypePtr type;
+
+public:
+	String getName() const override { return "quantilesExact"; }
+
+	DataTypePtr getReturnType() const override
+	{
+		return new DataTypeArray(type);
+	}
+
+	void setArgument(const DataTypePtr & argument)
+	{
+		type = argument;
+	}
+
+	void setParameters(const Array & params) override
+	{
+		if (params.empty())
+			throw Exception("Aggregate function " + getName() + " requires at least one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
+
+		size_t size = params.size();
+		levels.resize(size);
+
+		for (size_t i = 0; i < size; ++i)
+			levels[i] = apply_visitor(FieldVisitorConvertToNumber<Float64>(), params[i]);
+	}
+
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	{
+		this->data(place).array.push_back(static_cast<const ColumnVector<T> &>(column).getData()[row_num]);
+	}
+
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
+	{
+		this->data(place).array.insert(this->data(rhs).array.begin(), this->data(rhs).array.end());
+	}
+
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
+	{
+		const auto & array = this->data(place).array;
+
+		size_t size = array.size();
+		writeVarUInt(size, buf);
+		buf.write(reinterpret_cast<const char *>(&array[0]), size * sizeof(array[0]));
+	}
+
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
+	{
+		auto & array = this->data(place).array;
+
+		size_t size = 0;
+		readVarUInt(size, buf);
+		size_t old_size = array.size();
+		array.resize(old_size + size);
+		buf.read(reinterpret_cast<char *>(&array[old_size]), size * sizeof(array[0]));
+	}
+
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
+	{
+		/// Сортировка массива не будет считаться нарушением константности.
+		auto & array = const_cast<typename AggregateFunctionQuantileExactData<T>::Array &>(this->data(place).array);
+
+		ColumnArray & arr_to = static_cast<ColumnArray &>(to);
+		ColumnArray::Offsets_t & offsets_to = arr_to.getOffsets();
+
+		size_t num_levels = levels.size();
+		offsets_to.push_back((offsets_to.size() == 0 ? 0 : offsets_to.back()) + num_levels);
+
+		typename ColumnVector<T>::Container_t & data_to = static_cast<ColumnVector<T> &>(arr_to.getData()).getData();
+
+		if (!array.empty())
+		{
+			size_t prev_n = 0;
+			for (const auto & level : levels)
+			{
+				size_t n = level < 1
+					? level * array.size()
+					: (array.size() - 1);
+
+				std::nth_element(array.begin() + prev_n, array.begin() + n, array.end());
+
+				data_to.push_back(array[n]);
+				prev_n = n;
+			}
+		}
+		else
+		{
+			for (size_t i = 0; i < num_levels; ++i)
+				data_to.push_back(T());
+		}
+	}
+};
+
+}

dbms/include/DB/AggregateFunctions/AggregateFunctionQuantileExactWeighted.h

@@ -0,0 +1,286 @@
+#pragma once
+
+#include <DB/Common/HashTable/HashMap.h>
+
+#include <DB/Core/FieldVisitors.h>
+
+#include <DB/DataTypes/DataTypesNumberFixed.h>
+#include <DB/DataTypes/DataTypeArray.h>
+
+#include <DB/AggregateFunctions/IBinaryAggregateFunction.h>
+
+#include <DB/Columns/ColumnArray.h>
+
+
+namespace DB
+{
+
+
+/** В качестве состояния используется хэш-таблица вида: значение -> сколько раз встретилось.
+  */
+template <typename T>
+struct AggregateFunctionQuantileExactWeightedData
+{
+	using Key = T;
+	using Weight = UInt64;
+
+	/// При создании, хэш-таблица должна быть небольшой.
+	using Map = HashMap<
+		Key, Weight,
+		HashCRC32<Key>,
+		HashTableGrower<4>,
+		HashTableAllocatorWithStackMemory<sizeof(std::pair<Key, Weight>) * (1 << 3)>
+	>;
+
+	Map map;
+};
+
+
+/** Точно вычисляет квантиль по множеству значений, для каждого из которых задан вес - сколько раз значение встречалось.
+  * Можно рассматривать набор пар value, weight - как набор гистограмм,
+  *  в которых value - значение, округлённое до середины столбика, а weight - высота столбика.
+  * В качестве типа аргумента может быть только числовой тип (в том числе, дата и дата-с-временем).
+  * Тип результата совпадает с типом аргумента.
+  */
+template <typename ValueType, typename WeightType>
+class AggregateFunctionQuantileExactWeighted final
+	: public IBinaryAggregateFunction<
+		AggregateFunctionQuantileExactWeightedData<ValueType>,
+		AggregateFunctionQuantileExactWeighted<ValueType, WeightType>>
+{
+private:
+	double level;
+	DataTypePtr type;
+
+public:
+	AggregateFunctionQuantileExactWeighted(double level_ = 0.5) : level(level_) {}
+
+	String getName() const override { return "quantileExactWeighted"; }
+
+	DataTypePtr getReturnType() const override
+	{
+		return type;
+	}
+
+	void setArgumentsImpl(const DataTypes & arguments)
+	{
+		type = arguments[0];
+	}
+
+	void setParameters(const Array & params) override
+	{
+		if (params.size() != 1)
+			throw Exception("Aggregate function " + getName() + " requires exactly one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
+
+		level = apply_visitor(FieldVisitorConvertToNumber<Float64>(), params[0]);
+	}
+
+	void addImpl(AggregateDataPtr place, const IColumn & column_value, const IColumn & column_weight, size_t row_num) const
+	{
+		this->data(place)
+			.map[static_cast<const ColumnVector<ValueType> &>(column_value).getData()[row_num]]
+			+= static_cast<const ColumnVector<WeightType> &>(column_weight).getData()[row_num];
+	}
+
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
+	{
+		auto & map = this->data(place).map;
+		const auto & rhs_map = this->data(rhs).map;
+
+		for (const auto & pair : rhs_map)
+			map[pair.first] += pair.second;
+	}
+
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
+	{
+		this->data(place).map.write(buf);
+	}
+
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
+	{
+		typename AggregateFunctionQuantileExactWeightedData<ValueType>::Map::Reader reader(buf);
+
+		auto & map = this->data(place).map;
+		while (reader.next())
+		{
+			const auto & pair = reader.get();
+			map[pair.first] += pair.second;
+		}
+	}
+
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
+	{
+		auto & map = this->data(place).map;
+		size_t size = map.size();
+
+		if (0 == size)
+		{
+			static_cast<ColumnVector<ValueType> &>(to).getData().push_back(ValueType());
+			return;
+		}
+
+		/// Копируем данные во временный массив, чтобы получить нужный по порядку элемент.
+		using Pair = typename AggregateFunctionQuantileExactWeightedData<ValueType>::Map::value_type;
+		std::unique_ptr<Pair[]> array_holder(new Pair[size]);
+		Pair * array = array_holder.get();
+
+		size_t i = 0;
+		UInt64 sum_weight = 0;
+		for (const auto & pair : map)
+		{
+			sum_weight += pair.second;
+			array[i] = pair;
+			++i;
+		}
+
+		std::sort(array, array + size, [](const Pair & a, const Pair & b) { return a.first < b.first; });
+
+		UInt64 threshold = sum_weight * level;
+		UInt64 accumulated = 0;
+
+		const Pair * it = array;
+		const Pair * end = array + size;
+		while (it < end && accumulated < threshold)
+		{
+			accumulated += it->second;
+			++it;
+		}
+
+		if (it == end)
+			--it;
+
+		static_cast<ColumnVector<ValueType> &>(to).getData().push_back(it->first);
+	}
+};
+
+
+/** То же самое, но позволяет вычислить сразу несколько квантилей.
+  * Для этого, принимает в качестве параметров несколько уровней. Пример: quantilesExactWeighted(0.5, 0.8, 0.9, 0.95)(ConnectTiming, Weight).
+  * Возвращает массив результатов.
+  */
+template <typename ValueType, typename WeightType>
+class AggregateFunctionQuantilesExactWeighted final
+	: public IBinaryAggregateFunction<
+		AggregateFunctionQuantileExactWeightedData<ValueType>,
+		AggregateFunctionQuantilesExactWeighted<ValueType, WeightType>>
+{
+private:
+	using Levels = std::vector<double>;
+	Levels levels;
+	DataTypePtr type;
+
+public:
+	String getName() const override { return "quantilesExactWeighted"; }
+
+	DataTypePtr getReturnType() const override
+	{
+		return new DataTypeArray(type);
+	}
+
+	void setArgumentsImpl(const DataTypes & arguments)
+	{
+		type = arguments[0];
+	}
+
+	void setParameters(const Array & params) override
+	{
+		if (params.empty())
+			throw Exception("Aggregate function " + getName() + " requires at least one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
+
+		size_t size = params.size();
+		levels.resize(size);
+
+		for (size_t i = 0; i < size; ++i)
+			levels[i] = apply_visitor(FieldVisitorConvertToNumber<Float64>(), params[i]);
+	}
+
+	void addImpl(AggregateDataPtr place, const IColumn & column_value, const IColumn & column_weight, size_t row_num) const
+	{
+		this->data(place)
+			.map[static_cast<const ColumnVector<ValueType> &>(column_value).getData()[row_num]]
+			+= static_cast<const ColumnVector<WeightType> &>(column_weight).getData()[row_num];
+	}
+
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
+	{
+		auto & map = this->data(place).map;
+		const auto & rhs_map = this->data(rhs).map;
+
+		for (const auto & pair : rhs_map)
+			map[pair.first] += pair.second;
+	}
+
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
+	{
+		this->data(place).map.write(buf);
+	}
+
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
+	{
+		typename AggregateFunctionQuantileExactWeightedData<ValueType>::Map::Reader reader(buf);
+
+		auto & map = this->data(place).map;
+		while (reader.next())
+		{
+			const auto & pair = reader.get();
+			map[pair.first] += pair.second;
+		}
+	}
+
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
+	{
+		auto & map = this->data(place).map;
+		size_t size = map.size();
+
+		ColumnArray & arr_to = static_cast<ColumnArray &>(to);
+		ColumnArray::Offsets_t & offsets_to = arr_to.getOffsets();
+
+		size_t num_levels = levels.size();
+		offsets_to.push_back((offsets_to.size() == 0 ? 0 : offsets_to.back()) + num_levels);
+
+		typename ColumnVector<ValueType>::Container_t & data_to = static_cast<ColumnVector<ValueType> &>(arr_to.getData()).getData();
+
+		if (0 == size)
+		{
+			for (size_t i = 0; i < num_levels; ++i)
+				data_to.push_back(ValueType());
+			return;
+		}
+
+		/// Копируем данные во временный массив, чтобы получить нужный по порядку элемент.
+		using Pair = typename AggregateFunctionQuantileExactWeightedData<ValueType>::Map::value_type;
+		std::unique_ptr<Pair[]> array_holder(new Pair[size]);
+		Pair * array = array_holder.get();
+
+		size_t i = 0;
+		UInt64 sum_weight = 0;
+		for (const auto & pair : map)
+		{
+			sum_weight += pair.second;
+			array[i] = pair;
+			++i;
+		}
+
+		std::sort(array, array + size, [](const Pair & a, const Pair & b) { return a.first < b.first; });
+
+		UInt64 accumulated = 0;
+
+		const Pair * it = array;
+		const Pair * end = array + size;
+
+		for (const auto & level : levels)
+		{
+			UInt64 threshold = sum_weight * level;
+
+			while (it < end && accumulated < threshold)
+			{
+				accumulated += it->second;
+				++it;
+			}
+
+			data_to.push_back(it < end ? it->first : it[-1].first);
+		}
+	}
+};
+
+}

dbms/include/DB/AggregateFunctions/AggregateFunctionQuantileTiming.h

@@ -3,6 +3,7 @@
 #include <limits>
 
 #include <DB/Common/MemoryTracker.h>
+#include <DB/Common/HashTable/Hash.h>
 
 #include <DB/Core/FieldVisitors.h>
 
@@ -13,10 +14,10 @@
 #include <DB/DataTypes/DataTypeArray.h>
 
 #include <DB/AggregateFunctions/IUnaryAggregateFunction.h>
+#include <DB/AggregateFunctions/IBinaryAggregateFunction.h>
 
 #include <DB/Columns/ColumnArray.h>
 
-#include <stats/IntHash.h>
 #include <ext/range.hpp>
 
 
@@ -549,9 +550,9 @@ private:
 public:
 	AggregateFunctionQuantileTiming(double level_ = 0.5) : level(level_) {}
 
-	String getName() const { return "quantileTiming"; }
+	String getName() const override { return "quantileTiming"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeFloat32;
 	}
@@ -560,7 +561,7 @@ public:
 	{
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		if (params.size() != 1)
 			throw Exception("Aggregate function " + getName() + " requires exactly one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
@@ -569,27 +570,27 @@ public:
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		this->data(place).insert(static_cast<const ColumnVector<ArgumentFieldType> &>(column).getData()[row_num]);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).merge(this->data(rhs));
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).serialize(buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		this->data(place).deserializeMerge(buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		static_cast<ColumnFloat32 &>(to).getData().push_back(this->data(place).getFloat(level));
 	}
@@ -607,18 +608,18 @@ private:
 public:
 	AggregateFunctionQuantileTimingWeighted(double level_ = 0.5) : level(level_) {}
 
-	String getName() const { return "quantileTimingWeighted"; }
+	String getName() const override { return "quantileTimingWeighted"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeFloat32;
 	}
 
-	void setArguments(const DataTypes & arguments)
+	void setArguments(const DataTypes & arguments) override
 	{
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		if (params.size() != 1)
 			throw Exception("Aggregate function " + getName() + " requires exactly one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
@@ -627,29 +628,29 @@ public:
 	}
 
 
-	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const
+	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override
 	{
 		this->data(place).insertWeighted(
 			static_cast<const ColumnVector<ArgumentFieldType> &>(*columns[0]).getData()[row_num],
 			static_cast<const ColumnVector<WeightFieldType> &>(*columns[1]).getData()[row_num]);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).merge(this->data(rhs));
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).serialize(buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		this->data(place).deserializeMerge(buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		static_cast<ColumnFloat32 &>(to).getData().push_back(this->data(place).getFloat(level));
 	}
@@ -668,9 +669,9 @@ private:
 	Levels levels;
 
 public:
-	String getName() const { return "quantilesTiming"; }
+	String getName() const override { return "quantilesTiming"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeArray(new DataTypeFloat32);
 	}
@@ -679,7 +680,7 @@ public:
 	{
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		if (params.empty())
 			throw Exception("Aggregate function " + getName() + " requires at least one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
@@ -692,27 +693,27 @@ public:
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		this->data(place).insert(static_cast<const ColumnVector<ArgumentFieldType> &>(column).getData()[row_num]);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).merge(this->data(rhs));
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).serialize(buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		this->data(place).deserializeMerge(buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		ColumnArray & arr_to = static_cast<ColumnArray &>(to);
 		ColumnArray::Offsets_t & offsets_to = arr_to.getOffsets();
@@ -730,25 +731,26 @@ public:
 
 
 template <typename ArgumentFieldType, typename WeightFieldType>
-class AggregateFunctionQuantilesTimingWeighted final : public IAggregateFunctionHelper<QuantileTiming>
+class AggregateFunctionQuantilesTimingWeighted final
+	: public IBinaryAggregateFunction<QuantileTiming, AggregateFunctionQuantilesTimingWeighted<ArgumentFieldType, WeightFieldType>>
 {
 private:
-	typedef std::vector<double> Levels;
+	using Levels = std::vector<double>;
 	Levels levels;
 
 public:
-	String getName() const { return "quantilesTimingWeighted"; }
+	String getName() const override { return "quantilesTimingWeighted"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeArray(new DataTypeFloat32);
 	}
 
-	void setArguments(const DataTypes & arguments)
+	void setArgumentsImpl(const DataTypes & arguments)
 	{
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		if (params.empty())
 			throw Exception("Aggregate function " + getName() + " requires at least one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
@@ -760,29 +762,29 @@ public:
 			levels[i] = apply_visitor(FieldVisitorConvertToNumber<Float64>(), params[i]);
 	}
 
-	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column_value, const IColumn & column_weight, size_t row_num) const
 	{
 		this->data(place).insertWeighted(
-			static_cast<const ColumnVector<ArgumentFieldType> &>(*columns[0]).getData()[row_num],
-			static_cast<const ColumnVector<WeightFieldType> &>(*columns[1]).getData()[row_num]);
+			static_cast<const ColumnVector<ArgumentFieldType> &>(column_value).getData()[row_num],
+			static_cast<const ColumnVector<WeightFieldType> &>(column_weight).getData()[row_num]);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).merge(this->data(rhs));
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).serialize(buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		this->data(place).deserializeMerge(buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		ColumnArray & arr_to = static_cast<ColumnArray &>(to);
 		ColumnArray::Offsets_t & offsets_to = arr_to.getOffsets();

dbms/include/DB/AggregateFunctions/AggregateFunctionState.h

@@ -25,81 +25,82 @@ private:
 public:
 	AggregateFunctionState(AggregateFunctionPtr nested_) : nested_func_owner(nested_), nested_func(nested_func_owner.get()) {}
 
-	String getName() const
+	String getName() const override
 	{
 		return nested_func->getName() + "State";
 	}
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeAggregateFunction(nested_func_owner, arguments, params);
 	}
 
-	void setArguments(const DataTypes & arguments_)
+	void setArguments(const DataTypes & arguments_) override
 	{
 		arguments = arguments_;
 		nested_func->setArguments(arguments);
 	}
 
-	void setParameters(const Array & params_)
+	void setParameters(const Array & params_) override
 	{
 		params = params_;
 		nested_func->setParameters(params);
 	}
 
-	void create(AggregateDataPtr place) const
+	void create(AggregateDataPtr place) const override
 	{
 		nested_func->create(place);
 	}
 
-	void destroy(AggregateDataPtr place) const noexcept
+	void destroy(AggregateDataPtr place) const noexcept override
 	{
 		nested_func->destroy(place);
 	}
 
-	bool hasTrivialDestructor() const
+	bool hasTrivialDestructor() const override
 	{
 		return nested_func->hasTrivialDestructor();
 	}
 
-	size_t sizeOfData() const
+	size_t sizeOfData() const override
 	{
 		return nested_func->sizeOfData();
 	}
 
-	size_t alignOfData() const
+	size_t alignOfData() const override
 	{
 		return nested_func->alignOfData();
 	}
 
-	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const
+	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override
 	{
 		nested_func->add(place, columns, row_num);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		nested_func->merge(place, rhs);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		nested_func->serialize(place, buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		nested_func->deserializeMerge(place, buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		static_cast<ColumnAggregateFunction &>(to).getData().push_back(const_cast<AggregateDataPtr>(place));
 	}
 
 	/// Аггрегатная функция или состояние аггрегатной функции.
-	bool isState() const { return true; }
+	bool isState() const override { return true; }
 
+	AggregateFunctionPtr getNestedFunction() const { return nested_func_owner; }
 };
 
 }

dbms/include/DB/AggregateFunctions/AggregateFunctionSum.h

@@ -25,9 +25,9 @@ template <typename T>
 class AggregateFunctionSum final : public IUnaryAggregateFunction<AggregateFunctionSumData<typename NearestFieldType<T>::Type>, AggregateFunctionSum<T> >
 {
 public:
-	String getName() const { return "sum"; }
+	String getName() const override { return "sum"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new typename DataTypeFromFieldType<typename NearestFieldType<T>::Type>::Type;
 	}
@@ -40,29 +40,29 @@ public:
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		this->data(place).sum += static_cast<const ColumnVector<T> &>(column).getData()[row_num];
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).sum += this->data(rhs).sum;
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		writeBinary(this->data(place).sum, buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		typename NearestFieldType<T>::Type tmp;
 		readBinary(tmp, buf);
 		this->data(place).sum += tmp;
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		static_cast<ColumnVector<typename NearestFieldType<T>::Type> &>(to).getData().push_back(this->data(place).sum);
 	}

dbms/include/DB/AggregateFunctions/AggregateFunctionUniq.h

@@ -3,7 +3,7 @@
 #include <city.h>
 #include <type_traits>
 
-#include <stats/UniquesHashSet.h>
+#include <DB/AggregateFunctions/UniquesHashSet.h>
 
 #include <DB/IO/WriteHelpers.h>
 #include <DB/IO/ReadHelpers.h>
@@ -11,6 +11,7 @@
 
 #include <DB/DataTypes/DataTypesNumberFixed.h>
 #include <DB/DataTypes/DataTypeString.h>
+#include <DB/DataTypes/DataTypeTuple.h>
 
 #include <DB/Interpreters/AggregationCommon.h>
 #include <DB/Common/HashTable/HashSet.h>
@@ -18,9 +19,11 @@
 #include <DB/Common/CombinedCardinalityEstimator.h>
 
 #include <DB/Columns/ColumnString.h>
+#include <DB/Columns/ColumnTuple.h>
 
 #include <DB/AggregateFunctions/IUnaryAggregateFunction.h>
 #include <DB/AggregateFunctions/UniqCombinedBiasData.h>
+#include <DB/AggregateFunctions/UniqVariadicHash.h>
 
 
 namespace DB
@@ -30,12 +33,22 @@ namespace DB
 
 struct AggregateFunctionUniqUniquesHashSetData
 {
-	typedef UniquesHashSet<DefaultHash<UInt64> > Set;
+	typedef UniquesHashSet<DefaultHash<UInt64>> Set;
 	Set set;
 
 	static String getName() { return "uniq"; }
 };
 
+/// Для функции, принимающей несколько аргументов. Такая функция сама заранее их хэширует, поэтому здесь используется TrivialHash.
+struct AggregateFunctionUniqUniquesHashSetDataForVariadic
+{
+	typedef UniquesHashSet<TrivialHash> Set;
+	Set set;
+
+	static String getName() { return "uniq"; }
+};
+
+
 /// uniqHLL12
 
 template <typename T>
@@ -56,6 +69,15 @@ struct AggregateFunctionUniqHLL12Data<String>
 	static String getName() { return "uniqHLL12"; }
 };
 
+struct AggregateFunctionUniqHLL12DataForVariadic
+{
+	typedef HyperLogLogWithSmallSetOptimization<UInt64, 16, 12, TrivialHash> Set;
+	Set set;
+
+	static String getName() { return "uniqHLL12"; }
+};
+
+
 /// uniqExact
 
 template <typename T>
@@ -66,7 +88,7 @@ struct AggregateFunctionUniqExactData
 	/// При создании, хэш-таблица должна быть небольшой.
 	typedef HashSet<
 		Key,
-		DefaultHash<Key>,
+		HashCRC32<Key>,
 		HashTableGrower<4>,
 		HashTableAllocatorWithStackMemory<sizeof(Key) * (1 << 4)>
 	> Set;
@@ -234,7 +256,7 @@ struct OneAdder<T, Data, typename std::enable_if<
 	std::is_same<Data, AggregateFunctionUniqHLL12Data<T> >::value>::type>
 {
 	template <typename T2 = T>
-	static void addOne(Data & data, const IColumn & column, size_t row_num,
+	static void addImpl(Data & data, const IColumn & column, size_t row_num,
 		typename std::enable_if<!std::is_same<T2, String>::value>::type * = nullptr)
 	{
 		const auto & value = static_cast<const ColumnVector<T2> &>(column).getData()[row_num];
@@ -242,7 +264,7 @@ struct OneAdder<T, Data, typename std::enable_if<
 	}
 
 	template <typename T2 = T>
-	static void addOne(Data & data, const IColumn & column,	size_t row_num,
+	static void addImpl(Data & data, const IColumn & column,	size_t row_num,
 		typename std::enable_if<std::is_same<T2, String>::value>::type * = nullptr)
 	{
 		StringRef value = column.getDataAt(row_num);
@@ -258,7 +280,7 @@ struct OneAdder<T, Data, typename std::enable_if<
 	std::is_same<Data, AggregateFunctionUniqCombinedData<T> >::value>::type>
 {
 	template <typename T2 = T>
-	static void addOne(Data & data, const IColumn & column, size_t row_num,
+	static void addImpl(Data & data, const IColumn & column, size_t row_num,
 		typename std::enable_if<!std::is_same<T2, String>::value>::type * = nullptr)
 	{
 		const auto & value = static_cast<const ColumnVector<T2> &>(column).getData()[row_num];
@@ -266,7 +288,7 @@ struct OneAdder<T, Data, typename std::enable_if<
 	}
 
 	template <typename T2 = T>
-	static void addOne(Data & data, const IColumn & column,	size_t row_num,
+	static void addImpl(Data & data, const IColumn & column,	size_t row_num,
 		typename std::enable_if<std::is_same<T2, String>::value>::type * = nullptr)
 	{
 		StringRef value = column.getDataAt(row_num);
@@ -279,14 +301,14 @@ struct OneAdder<T, Data, typename std::enable_if<
 	std::is_same<Data, AggregateFunctionUniqExactData<T> >::value>::type>
 {
 	template <typename T2 = T>
-	static void addOne(Data & data, const IColumn & column, size_t row_num,
+	static void addImpl(Data & data, const IColumn & column, size_t row_num,
 		typename std::enable_if<!std::is_same<T2, String>::value>::type * = nullptr)
 	{
 		data.set.insert(static_cast<const ColumnVector<T2> &>(column).getData()[row_num]);
 	}
 
 	template <typename T2 = T>
-	static void addOne(Data & data, const IColumn & column, size_t row_num,
+	static void addImpl(Data & data, const IColumn & column, size_t row_num,
 		typename std::enable_if<std::is_same<T2, String>::value>::type * = nullptr)
 	{
 		StringRef value = column.getDataAt(row_num);
@@ -303,14 +325,14 @@ struct OneAdder<T, Data, typename std::enable_if<
 }
 
 
-/// Приближённо вычисляет количество различных значений.
+/// Приближённо или точно вычисляет количество различных значений.
 template <typename T, typename Data>
 class AggregateFunctionUniq final : public IUnaryAggregateFunction<Data, AggregateFunctionUniq<T, Data> >
 {
 public:
-	String getName() const { return Data::getName(); }
+	String getName() const override { return Data::getName(); }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeUInt64;
 	}
@@ -319,27 +341,82 @@ public:
 	{
 	}
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
-		detail::OneAdder<T, Data>::addOne(this->data(place), column, row_num);
+		detail::OneAdder<T, Data>::addImpl(this->data(place), column, row_num);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).set.merge(this->data(rhs).set);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).set.write(buf);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		this->data(place).set.readAndMerge(buf);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
+	{
+		static_cast<ColumnUInt64 &>(to).getData().push_back(this->data(place).set.size());
+	}
+};
+
+
+/** Для нескольких аргументов. Для вычисления, хэширует их.
+  * Можно передать несколько аргументов как есть; также можно передать один аргумент - кортеж.
+  * Но (для возможности эффективной реализации), нельзя передать несколько аргументов, среди которых есть кортежи.
+  */
+template <typename Data, bool argument_is_tuple>
+class AggregateFunctionUniqVariadic final : public IAggregateFunctionHelper<Data>
+{
+private:
+	static constexpr bool is_exact = std::is_same<Data, AggregateFunctionUniqExactData<String>>::value;
+
+	size_t num_args = 0;
+
+public:
+	String getName() const override { return Data::getName(); }
+
+	DataTypePtr getReturnType() const override
+	{
+		return new DataTypeUInt64;
+	}
+
+	void setArguments(const DataTypes & arguments) override
+	{
+		if (argument_is_tuple)
+			num_args = typeid_cast<const DataTypeTuple &>(*arguments[0]).getElements().size();
+		else
+			num_args = arguments.size();
+	}
+
+	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override
+	{
+		this->data(place).set.insert(UniqVariadicHash<is_exact, argument_is_tuple>::apply(num_args, columns, row_num));
+	}
+
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
+	{
+		this->data(place).set.merge(this->data(rhs).set);
+	}
+
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
+	{
+		this->data(place).set.write(buf);
+	}
+
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
+	{
+		this->data(place).set.readAndMerge(buf);
+	}
+
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		static_cast<ColumnUInt64 &>(to).getData().push_back(this->data(place).set.size());
 	}

dbms/include/DB/AggregateFunctions/AggregateFunctionUniqUpTo.h

@@ -2,7 +2,9 @@
 
 #include <DB/Core/FieldVisitors.h>
 #include <DB/AggregateFunctions/IUnaryAggregateFunction.h>
+#include <DB/AggregateFunctions/UniqVariadicHash.h>
 #include <DB/DataTypes/DataTypesNumberFixed.h>
+#include <DB/DataTypes/DataTypeTuple.h>
 
 
 namespace DB
@@ -102,7 +104,7 @@ struct __attribute__((__packed__)) AggregateFunctionUniqUpToData
 	}
 
 
-	void addOne(const IColumn & column, size_t row_num, UInt8 threshold)
+	void addImpl(const IColumn & column, size_t row_num, UInt8 threshold)
 	{
 		insert(static_cast<const ColumnVector<T> &>(column).getData()[row_num], threshold);
 	}
@@ -113,7 +115,7 @@ struct __attribute__((__packed__)) AggregateFunctionUniqUpToData
 template <>
 struct AggregateFunctionUniqUpToData<String> : AggregateFunctionUniqUpToData<UInt64>
 {
-	void addOne(const IColumn & column, size_t row_num, UInt8 threshold)
+	void addImpl(const IColumn & column, size_t row_num, UInt8 threshold)
 	{
 		/// Имейте ввиду, что вычисление приближённое.
 		StringRef value = column.getDataAt(row_num);
@@ -131,14 +133,14 @@ private:
 	UInt8 threshold = 5;	/// Значение по-умолчанию, если параметр не указан.
 
 public:
-	size_t sizeOfData() const
+	size_t sizeOfData() const override
 	{
 		return sizeof(AggregateFunctionUniqUpToData<T>) + sizeof(T) * threshold;
 	}
 
-	String getName() const { return "uniqUpTo"; }
+	String getName() const override { return "uniqUpTo"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return new DataTypeUInt64;
 	}
@@ -147,7 +149,7 @@ public:
 	{
 	}
 
-	void setParameters(const Array & params)
+	void setParameters(const Array & params) override
 	{
 		if (params.size() != 1)
 			throw Exception("Aggregate function " + getName() + " requires exactly one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
@@ -161,27 +163,100 @@ public:
 		threshold = threshold_param;
 	}
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
-		this->data(place).addOne(column, row_num, threshold);
+		this->data(place).addImpl(column, row_num, threshold);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).merge(this->data(rhs), threshold);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).write(buf, threshold);
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		this->data(place).readAndMerge(buf, threshold);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
+	{
+		static_cast<ColumnUInt64 &>(to).getData().push_back(this->data(place).size());
+	}
+};
+
+
+/** Для нескольких аргументов. Для вычисления, хэширует их.
+  * Можно передать несколько аргументов как есть; также можно передать один аргумент - кортеж.
+  * Но (для возможности эффективной реализации), нельзя передать несколько аргументов, среди которых есть кортежи.
+  */
+template <bool argument_is_tuple>
+class AggregateFunctionUniqUpToVariadic final : public IAggregateFunctionHelper<AggregateFunctionUniqUpToData<UInt64>>
+{
+private:
+	size_t num_args = 0;
+	UInt8 threshold = 5;	/// Значение по-умолчанию, если параметр не указан.
+
+public:
+	size_t sizeOfData() const override
+	{
+		return sizeof(AggregateFunctionUniqUpToData<UInt64>) + sizeof(UInt64) * threshold;
+	}
+
+	String getName() const override { return "uniqUpTo"; }
+
+	DataTypePtr getReturnType() const override
+	{
+		return new DataTypeUInt64;
+	}
+
+	void setArguments(const DataTypes & arguments) override
+	{
+		if (argument_is_tuple)
+			num_args = typeid_cast<const DataTypeTuple &>(*arguments[0]).getElements().size();
+		else
+			num_args = arguments.size();
+	}
+
+	void setParameters(const Array & params) override
+	{
+		if (params.size() != 1)
+			throw Exception("Aggregate function " + getName() + " requires exactly one parameter.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
+
+		UInt64 threshold_param = apply_visitor(FieldVisitorConvertToNumber<UInt64>(), params[0]);
+
+		if (threshold_param > uniq_upto_max_threshold)
+			throw Exception("Too large parameter for aggregate function " + getName() + ". Maximum: " + toString(uniq_upto_max_threshold),
+				ErrorCodes::ARGUMENT_OUT_OF_BOUND);
+
+		threshold = threshold_param;
+	}
+
+	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override
+	{
+		this->data(place).insert(UniqVariadicHash<false, argument_is_tuple>::apply(num_args, columns, row_num), threshold);
+	}
+
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
+	{
+		this->data(place).merge(this->data(rhs), threshold);
+	}
+
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
+	{
+		this->data(place).write(buf, threshold);
+	}
+
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
+	{
+		this->data(place).readAndMerge(buf, threshold);
+	}
+
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		static_cast<ColumnUInt64 &>(to).getData().push_back(this->data(place).size());
 	}

dbms/include/DB/AggregateFunctions/AggregateFunctionsArgMinMax.h

@@ -27,14 +27,14 @@ private:
 	DataTypePtr type_val;
 
 public:
-	String getName() const { return (0 == strcmp(Data::ValueData_t::name(), "min")) ? "argMin" : "argMax"; }
+	String getName() const override { return (0 == strcmp(Data::ValueData_t::name(), "min")) ? "argMin" : "argMax"; }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return type_res;
 	}
 
-	void setArguments(const DataTypes & arguments)
+	void setArguments(const DataTypes & arguments) override
 	{
 		if (arguments.size() != 2)
 			throw Exception("Aggregate function " + getName() + " requires exactly two arguments.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
@@ -43,25 +43,25 @@ public:
 		type_val = arguments[1];
 	}
 
-	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const
+	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override
 	{
 		if (this->data(place).value.changeIfBetter(*columns[1], row_num))
 			this->data(place).result.change(*columns[0], row_num);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		if (this->data(place).value.changeIfBetter(this->data(rhs).value))
 			this->data(place).result.change(this->data(rhs).result);
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).result.write(buf, *type_res.get());
 		this->data(place).value.write(buf, *type_val.get());
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		Data rhs;	/// Для строчек не очень оптимально, так как может делаться одна лишняя аллокация.
 
@@ -72,7 +72,7 @@ public:
 			this->data(place).result.change(rhs.result);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		this->data(place).result.insertResultInto(to);
 	}

dbms/include/DB/AggregateFunctions/AggregateFunctionsMinMaxAny.h

@@ -5,6 +5,7 @@
 
 #include <DB/Columns/ColumnVector.h>
 #include <DB/Columns/ColumnString.h>
+#include <DB/DataTypes/DataTypeAggregateFunction.h>
 
 #include <DB/AggregateFunctions/IUnaryAggregateFunction.h>
 
@@ -531,9 +532,9 @@ private:
 	DataTypePtr type;
 
 public:
-	String getName() const { return Data::name(); }
+	String getName() const override { return Data::name(); }
 
-	DataTypePtr getReturnType() const
+	DataTypePtr getReturnType() const override
 	{
 		return type;
 	}
@@ -541,25 +542,28 @@ public:
 	void setArgument(const DataTypePtr & argument)
 	{
 		type = argument;
+
+		if (typeid_cast<const DataTypeAggregateFunction *>(type.get()))
+			throw Exception("Illegal type " + type->getName() + " of argument of aggregate function " + getName(), ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
 	}
 
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		this->data(place).changeIfBetter(column, row_num);
 	}
 
-	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
+	void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
 	{
 		this->data(place).changeIfBetter(this->data(rhs));
 	}
 
-	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
+	void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
 	{
 		this->data(place).write(buf, *type.get());
 	}
 
-	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
+	void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
 	{
 		Data rhs;	/// Для строчек не очень оптимально, так как может делаться одна лишняя аллокация.
 		rhs.read(buf, *type.get());
@@ -567,7 +571,7 @@ public:
 		this->data(place).changeIfBetter(rhs);
 	}
 
-	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
+	void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
 	{
 		this->data(place).insertResultInto(to);
 	}

dbms/include/DB/AggregateFunctions/AggregateFunctionsStatistics.h

@@ -122,14 +122,14 @@ public:
 		return new DataTypeFloat64;
 	}
 
-	void setArgument(const DataTypePtr & argument) override
+	void setArgument(const DataTypePtr & argument)
 	{
 		if (!argument->behavesAsNumber())
 			throw Exception("Illegal type " + argument->getName() + " of argument for aggregate function " + getName(),
 				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
 	}
 
-	void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const
 	{
 		this->data(place).update(column, row_num);
 	}
@@ -400,7 +400,7 @@ public:
 				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
 	}
 
-	void addOne(AggregateDataPtr place, const IColumn & column_left, const IColumn & column_right, size_t row_num) const
+	void addImpl(AggregateDataPtr place, const IColumn & column_left, const IColumn & column_right, size_t row_num) const
 	{
 		this->data(place).update(column_left, column_right, row_num);
 	}

dbms/include/DB/AggregateFunctions/IAggregateFunction.h

@@ -104,28 +104,28 @@ protected:
 	static const Data & data(ConstAggregateDataPtr place) 	{ return *reinterpret_cast<const Data*>(place); }
 
 public:
-	void create(AggregateDataPtr place) const
+	void create(AggregateDataPtr place) const override
 	{
 		new (place) Data;
 	}
 
-	void destroy(AggregateDataPtr place) const noexcept
+	void destroy(AggregateDataPtr place) const noexcept override
 	{
 		data(place).~Data();
 	}
 
-	bool hasTrivialDestructor() const
+	bool hasTrivialDestructor() const override
 	{
 		return __has_trivial_destructor(Data);
 	}
 
-	size_t sizeOfData() const
+	size_t sizeOfData() const override
 	{
 		return sizeof(Data);
 	}
 
 	/// NOTE: Сейчас не используется (структуры с состоянием агрегации кладутся без выравнивания).
-	size_t alignOfData() const
+	size_t alignOfData() const override
 	{
 		return __alignof__(Data);
 	}

dbms/include/DB/AggregateFunctions/IBinaryAggregateFunction.h

@@ -8,11 +8,12 @@ namespace DB
 template <typename T, typename Derived>
 class IBinaryAggregateFunction : public IAggregateFunctionHelper<T>
 {
+private:
 	Derived & getDerived() { return static_cast<Derived &>(*this); }
 	const Derived & getDerived() const { return static_cast<const Derived &>(*this); }
 
 public:
-	void setArguments(const DataTypes & arguments)
+	void setArguments(const DataTypes & arguments) override final
 	{
 		if (arguments.size() != 2)
 			throw Exception{
@@ -23,9 +24,9 @@ public:
 		getDerived().setArgumentsImpl(arguments);
 	}
 
-	void add(AggregateDataPtr place, const IColumn ** columns, const size_t row_num) const
+	void add(AggregateDataPtr place, const IColumn ** columns, const size_t row_num) const override final
 	{
-		getDerived().addOne(place, *columns[0], *columns[1], row_num);
+		getDerived().addImpl(place, *columns[0], *columns[1], row_num);
 	}
 };
 

dbms/include/DB/AggregateFunctions/INullaryAggregateFunction.h

@@ -11,9 +11,13 @@ namespace DB
 template <typename T, typename Derived>
 class INullaryAggregateFunction : public IAggregateFunctionHelper<T>
 {
+private:
+	Derived & getDerived() { return static_cast<Derived &>(*this); }
+	const Derived & getDerived() const { return static_cast<const Derived &>(*this); }
+
 public:
 	/// Получить тип результата по типам аргументов. Если функция неприменима для данных аргументов - кинуть исключение.
-	void setArguments(const DataTypes & arguments)
+	void setArguments(const DataTypes & arguments) override final
 	{
 		if (arguments.size() != 0)
 			throw Exception("Passed " + toString(arguments.size()) + " arguments to nullary aggregate function " + this->getName(),
@@ -21,13 +25,13 @@ public:
 	}
 
 	/// Добавить значение.
-	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const
+	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override final
 	{
-		static_cast<const Derived &>(*this).addZero(place);
+		getDerived().addImpl(place);
 	}
 
 	/** Реализуйте это в классе-наследнике:
-	  * void addZero(AggregateDataPtr place) const;
+	  * void addImpl(AggregateDataPtr place) const;
 	  */
 };
 

dbms/include/DB/AggregateFunctions/IUnaryAggregateFunction.h

@@ -11,25 +11,29 @@ namespace DB
 template <typename T, typename Derived>
 class IUnaryAggregateFunction : public IAggregateFunctionHelper<T>
 {
+private:
+	Derived & getDerived() { return static_cast<Derived &>(*this); }
+	const Derived & getDerived() const { return static_cast<const Derived &>(*this); }
+
 public:
-	void setArguments(const DataTypes & arguments)
+	void setArguments(const DataTypes & arguments) override final
 	{
 		if (arguments.size() != 1)
 			throw Exception("Passed " + toString(arguments.size()) + " arguments to unary aggregate function " + this->getName(),
 				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
-		setArgument(arguments[0]);
+
+		getDerived().setArgument(arguments[0]);
 	}
 
-	virtual void setArgument(const DataTypePtr & argument) = 0;
-
 	/// Добавить значение.
-	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const
+	void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override final
 	{
-		static_cast<const Derived &>(*this).addOne(place, *columns[0], row_num);
+		getDerived().addImpl(place, *columns[0], row_num);
 	}
 
 	/** Реализуйте это в классе-наследнике:
-	  * void addOne(AggregateDataPtr place, const IColumn & column, size_t row_num) const;
+	  * void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const;
+	  * void setArgument(const DataTypePtr & argument);
 	  */
 };
 

dbms/include/DB/AggregateFunctions/ReservoirSampler.h

@@ -0,0 +1,237 @@
+#pragma once
+
+#include <limits>
+#include <algorithm>
+#include <climits>
+#include <sstream>
+#include <common/Common.h>
+#include <DB/IO/ReadBuffer.h>
+#include <DB/IO/ReadHelpers.h>
+#include <DB/IO/WriteHelpers.h>
+#include <DB/Common/PODArray.h>
+#include <Poco/Exception.h>
+#include <boost/random.hpp>
+
+
+/// Реализация алгоритма Reservoir Sampling. Инкрементально выбирает из добавленных объектов случайное подмножество размера sample_count.
+/// Умеет приближенно получать квантили.
+/// Вызов quantile занимает O(sample_count log sample_count), если после предыдущего вызова quantile был хотя бы один вызов insert. Иначе, O(1).
+/// То есть, имеет смысл сначала добавлять, потом получать квантили, не добавляя.
+
+const size_t DEFAULT_SAMPLE_COUNT = 8192;
+
+/// Что делать, если нет ни одного значения - кинуть исключение, или вернуть 0 или NaN в случае double?
+namespace ReservoirSamplerOnEmpty
+{
+	enum Enum
+	{
+		THROW,
+		RETURN_NAN_OR_ZERO,
+	};
+}
+
+template<typename ResultType, bool IsFloatingPoint>
+struct NanLikeValueConstructor
+{
+	static ResultType getValue()
+	{
+		return std::numeric_limits<ResultType>::quiet_NaN();
+	}
+};
+template<typename ResultType>
+struct NanLikeValueConstructor<ResultType, false>
+{
+	static ResultType getValue()
+	{
+		return ResultType();
+	}
+};
+
+template<typename T, ReservoirSamplerOnEmpty::Enum OnEmpty = ReservoirSamplerOnEmpty::THROW, typename Comparer = std::less<T> >
+class ReservoirSampler
+{
+public:
+	ReservoirSampler(size_t sample_count_ = DEFAULT_SAMPLE_COUNT)
+		: sample_count(sample_count_)
+	{
+		rng.seed(123456);
+	}
+
+	void clear()
+	{
+		samples.clear();
+		sorted = false;
+		total_values = 0;
+		rng.seed(123456);
+	}
+
+	void insert(const T & v)
+	{
+		sorted = false;
+		++total_values;
+		if (samples.size() < sample_count)
+		{
+			samples.push_back(v);
+		}
+		else
+		{
+			UInt64 rnd = genRandom(total_values);
+			if (rnd < sample_count)
+				samples[rnd] = v;
+		}
+	}
+
+	size_t size() const
+	{
+		return total_values;
+	}
+
+	T quantileNearest(double level)
+	{
+		if (samples.empty())
+			return onEmpty<T>();
+
+		sortIfNeeded();
+
+		double index = level * (samples.size() - 1);
+		size_t int_index = static_cast<size_t>(index + 0.5);
+		int_index = std::max(0LU, std::min(samples.size() - 1, int_index));
+		return samples[int_index];
+	}
+
+	/** Если T не числовой тип, использование этого метода вызывает ошибку компиляции,
+	  *  но использование класса ошибки не вызывает. SFINAE.
+	  */
+	double quantileInterpolated(double level)
+	{
+		if (samples.empty())
+			return onEmpty<double>();
+
+		sortIfNeeded();
+
+		double index = std::max(0., std::min(samples.size() - 1., level * (samples.size() - 1)));
+
+		/// Чтобы получить значение по дробному индексу линейно интерполируем между соседними значениями.
+		size_t left_index = static_cast<size_t>(index);
+		size_t right_index = left_index + 1;
+		if (right_index == samples.size())
+			return samples[left_index];
+
+		double left_coef = right_index - index;
+		double right_coef = index - left_index;
+
+		return samples[left_index] * left_coef + samples[right_index] * right_coef;
+	}
+
+	void merge(const ReservoirSampler<T, OnEmpty> & b)
+	{
+		if (sample_count != b.sample_count)
+			throw Poco::Exception("Cannot merge ReservoirSampler's with different sample_count");
+		sorted = false;
+
+		if (b.total_values <= sample_count)
+		{
+			for (size_t i = 0; i < b.samples.size(); ++i)
+				insert(b.samples[i]);
+		}
+		else if (total_values <= sample_count)
+		{
+			Array from = std::move(samples);
+			samples.assign(b.samples.begin(), b.samples.end());
+			total_values = b.total_values;
+			for (size_t i = 0; i < from.size(); ++i)
+				insert(from[i]);
+		}
+		else
+		{
+			randomShuffle(samples);
+			total_values += b.total_values;
+			for (size_t i = 0; i < sample_count; ++i)
+			{
+				UInt64 rnd = genRandom(total_values);
+				if (rnd < b.total_values)
+					samples[i] = b.samples[i];
+			}
+		}
+	}
+
+	void read(DB::ReadBuffer & buf)
+	{
+		DB::readIntBinary<size_t>(sample_count, buf);
+		DB::readIntBinary<size_t>(total_values, buf);
+		samples.resize(std::min(total_values, sample_count));
+
+		std::string rng_string;
+		DB::readStringBinary(rng_string, buf);
+		std::istringstream rng_stream(rng_string);
+		rng_stream >> rng;
+
+		for (size_t i = 0; i < samples.size(); ++i)
+			DB::readBinary(samples[i], buf);
+
+		sorted = false;
+	}
+
+	void write(DB::WriteBuffer & buf) const
+	{
+		DB::writeIntBinary<size_t>(sample_count, buf);
+		DB::writeIntBinary<size_t>(total_values, buf);
+
+		std::ostringstream rng_stream;
+		rng_stream << rng;
+		DB::writeStringBinary(rng_stream.str(), buf);
+
+		for (size_t i = 0; i < std::min(sample_count, total_values); ++i)
+			DB::writeBinary(samples[i], buf);
+	}
+
+private:
+	friend void qdigest_test(int normal_size, UInt64 value_limit, const std::vector<UInt64> & values, int queries_count, bool verbose);
+	friend void rs_perf_test();
+
+	/// Будем выделять немного памяти на стеке - чтобы избежать аллокаций, когда есть много объектов с маленьким количеством элементов.
+	static constexpr size_t bytes_on_stack = 64;
+	using Array = DB::PODArray<T, bytes_on_stack / sizeof(T), AllocatorWithStackMemory<Allocator<false>, bytes_on_stack>>;
+
+	size_t sample_count;
+	size_t total_values = 0;
+	Array samples;
+	boost::taus88 rng;
+	bool sorted = false;
+
+
+	UInt64 genRandom(size_t lim)
+	{
+		/// При большом количестве значений будем генерировать случайные числа в несколько раз медленнее.
+		if (lim <= static_cast<UInt64>(rng.max()))
+			return static_cast<UInt32>(rng()) % static_cast<UInt32>(lim);
+		else
+			return (static_cast<UInt64>(rng()) * (static_cast<UInt64>(rng.max()) + 1ULL) + static_cast<UInt64>(rng())) % lim;
+	}
+
+	void randomShuffle(Array & v)
+	{
+		for (size_t i = 1; i < v.size(); ++i)
+		{
+			size_t j = genRandom(i + 1);
+			std::swap(v[i], v[j]);
+		}
+	}
+
+	void sortIfNeeded()
+	{
+		if (sorted)
+			return;
+		sorted = true;
+		std::sort(samples.begin(), samples.end(), Comparer());
+	}
+
+	template <typename ResultType>
+	ResultType onEmpty() const
+	{
+		if (OnEmpty == ReservoirSamplerOnEmpty::THROW)
+			throw Poco::Exception("Quantile of empty ReservoirSampler");
+		else
+			return NanLikeValueConstructor<ResultType, std::is_floating_point<ResultType>::value>::getValue();
+	}
+};

dbms/include/DB/AggregateFunctions/ReservoirSamplerDeterministic.h

@@ -1,16 +1,16 @@
 #pragma once
 
 #include <limits>
-#include <vector>
 #include <algorithm>
 #include <climits>
 #include <sstream>
-#include <stats/ReservoirSampler.h>
+#include <DB/AggregateFunctions/ReservoirSampler.h>
 #include <common/Common.h>
 #include <DB/Common/HashTable/Hash.h>
 #include <DB/IO/ReadBuffer.h>
 #include <DB/IO/ReadHelpers.h>
 #include <DB/IO/WriteHelpers.h>
+#include <DB/Common/PODArray.h>
 #include <Poco/Exception.h>
 #include <boost/random.hpp>
 
@@ -150,13 +150,15 @@ public:
 	}
 
 private:
-	friend void rs_perf_test();
-	friend void qdigest_test(int, UInt64, const std::vector<UInt64> &, int, bool);
+	/// Будем выделять немного памяти на стеке - чтобы избежать аллокаций, когда есть много объектов с маленьким количеством элементов.
+	static constexpr size_t bytes_on_stack = 64;
+	using Element = std::pair<T, UInt32>;
+	using Array = DB::PODArray<Element, bytes_on_stack / sizeof(Element), AllocatorWithStackMemory<Allocator<false>, bytes_on_stack>>;
 
 	size_t sample_count;
 	size_t total_values{};
 	bool sorted{};
-	std::vector<std::pair<T, UInt32>> samples;
+	Array samples;
 	UInt8 skip_degree{};
 
 	void insertImpl(const T & v, const UInt32 hash)

dbms/include/DB/AggregateFunctions/UniqVariadicHash.h

@@ -0,0 +1,136 @@
+#pragma once
+
+#include <city.h>
+#include <DB/Core/Defines.h>
+#include <DB/Common/SipHash.h>
+#include <DB/Common/UInt128.h>
+#include <DB/Columns/ColumnTuple.h>
+
+
+namespace DB
+{
+
+/** Хэширует набор аргументов агрегатной функции
+  *  для вычисления количества уникальных значений
+  *  и добавляет их в множество.
+  *
+  * Четыре варианта (2 x 2):
+  *
+  * - для приближённого вычисления, использует некриптографическую 64-битную хэш-функцию;
+  * - для точного вычисления, использует криптографическую 128-битную хэш-функцию;
+  *
+  * - для нескольких аргументов, переданных обычным способом;
+  * - для одного аргумента-кортежа.
+  */
+
+template <bool exact, bool for_tuple>
+struct UniqVariadicHash;
+
+
+template <>
+struct UniqVariadicHash<false, false>
+{
+	static inline UInt64 apply(size_t num_args, const IColumn ** columns, size_t row_num)
+	{
+		UInt64 hash;
+
+		const IColumn ** column = columns;
+		const IColumn ** columns_end = column + num_args;
+
+		{
+			StringRef value = (*column)->getDataAt(row_num);
+			hash = CityHash64(value.data, value.size);
+			++column;
+		}
+
+		while (column < columns_end)
+		{
+			StringRef value = (*column)->getDataAt(row_num);
+			hash = Hash128to64(uint128(CityHash64(value.data, value.size), hash));
+			++column;
+		}
+
+		return hash;
+	}
+};
+
+template <>
+struct UniqVariadicHash<false, true>
+{
+	static inline UInt64 apply(size_t num_args, const IColumn ** columns, size_t row_num)
+	{
+		UInt64 hash;
+
+		const Columns & tuple_columns = static_cast<const ColumnTuple *>(columns[0])->getColumns();
+
+		const ColumnPtr * column = tuple_columns.data();
+		const ColumnPtr * columns_end = column + num_args;
+
+		{
+			StringRef value = column->get()->getDataAt(row_num);
+			hash = CityHash64(value.data, value.size);
+			++column;
+		}
+
+		while (column < columns_end)
+		{
+			StringRef value = column->get()->getDataAt(row_num);
+			hash = Hash128to64(uint128(CityHash64(value.data, value.size), hash));
+			++column;
+		}
+
+		return hash;
+	}
+};
+
+template <>
+struct UniqVariadicHash<true, false>
+{
+	static inline UInt128 apply(size_t num_args, const IColumn ** columns, size_t row_num)
+	{
+		SipHash hash;
+
+		const IColumn ** column = columns;
+		const IColumn ** columns_end = column + num_args;
+
+		while (column < columns_end)
+		{
+			StringRef value = (*column)->getDataAt(row_num);
+			hash.update(reinterpret_cast<const char *>(&value.size), sizeof(value.size));
+			hash.update(value.data, value.size);
+			++column;
+		}
+
+		UInt128 key;
+		hash.get128(key.first, key.second);
+		return key;
+	}
+};
+
+template <>
+struct UniqVariadicHash<true, true>
+{
+	static inline UInt128 apply(size_t num_args, const IColumn ** columns, size_t row_num)
+	{
+		SipHash hash;
+
+		const Columns & tuple_columns = static_cast<const ColumnTuple *>(columns[0])->getColumns();
+
+		const ColumnPtr * column = tuple_columns.data();
+		const ColumnPtr * columns_end = column + num_args;
+
+		while (column < columns_end)
+		{
+			StringRef value = column->get()->getDataAt(row_num);
+			hash.update(reinterpret_cast<const char *>(&value.size), sizeof(value.size));
+			hash.update(value.data, value.size);
+			++column;
+		}
+
+		UInt128 key;
+		hash.get128(key.first, key.second);
+		return key;
+	}
+};
+
+}

dbms/include/DB/AggregateFunctions/UniquesHashSet.h

@@ -0,0 +1,540 @@
+#pragma once
+
+#include <math.h>
+
+#include <common/Common.h>
+
+#include <DB/IO/WriteBuffer.h>
+#include <DB/IO/WriteHelpers.h>
+#include <DB/IO/ReadBuffer.h>
+#include <DB/IO/ReadHelpers.h>
+#include <DB/IO/VarInt.h>
+
+#include <DB/Common/HashTable/HashTableAllocator.h>
+#include <DB/Common/HashTable/Hash.h>
+
+
+/** Приближённый рассчёт чего-угодно, как правило, построен по следующей схеме:
+  * - для рассчёта значения X используется некоторая структура данных;
+  * - в структуру данных добавляются не все значения, а только избранные (согласно некоторому критерию избранности);
+  * - после обработки всех элементов, структура данных находится в некотором состоянии S;
+  * - в качестве приближённого значения X возвращается значание, посчитанное по принципу максимального правдоподобия:
+  *   при каком реальном значении X, вероятность нахождения структуры данных в полученном состоянии S максимальна.
+  */
+
+/** В частности, то, что описано ниже, можно найти по названию BJKST algorithm.
+  */
+
+/** Очень простое хэш-множество для приближённого подсчёта количества уникальных значений.
+  * Работает так:
+  * - вставлять можно UInt64;
+  * - перед вставкой, сначала вычисляется хэш-функция UInt64 -> UInt32;
+  * - исходное значение не сохраняется (теряется);
+  * - далее все операции производятся с этими хэшами;
+  * - хэш таблица построена по схеме:
+  * -  open addressing (один буфер, позиция в буфере вычисляется взятием остатка от деления на его размер);
+  * -  linear probing (если в ячейке уже есть значение, то берётся ячейка, следующая за ней и т. д.);
+  * -  отсутствующее значение кодируется нулём; чтобы запомнить наличие в множестве нуля, используется отдельная переменная типа bool;
+  * -  рост буфера в 2 раза при заполнении более чем на 50%;
+  * - если в множестве больше UNIQUES_HASH_MAX_SIZE элементов, то из множества удаляются все элементы,
+  *   не делящиеся на 2, и затем все элементы, которые не делятся на 2, не вставляются в множество;
+  * - если ситуация повторяется, то берутся только элементы делящиеся на 4 и т. п.
+  * - метод size() возвращает приблизительное количество элементов, которые были вставлены в множество;
+  * - есть методы для быстрого чтения и записи в бинарный и текстовый вид.
+  */
+
+
+/// Максимальная степень размера буфера перед тем, как значения будут выкидываться
+#define UNIQUES_HASH_MAX_SIZE_DEGREE 			17
+
+/// Максимальное количество элементов перед тем, как значения будут выкидываться
+#define UNIQUES_HASH_MAX_SIZE 					(1 << (UNIQUES_HASH_MAX_SIZE_DEGREE - 1))
+
+/** Количество младших бит, использующихся для прореживания. Оставшиеся старшие биты используются для определения позиции в хэш-таблице.
+  * (старшие биты берутся потому что младшие будут постоянными после выкидывания части значений)
+  */
+#define UNIQUES_HASH_BITS_FOR_SKIP 			(32 - UNIQUES_HASH_MAX_SIZE_DEGREE)
+
+/// Начальная степень размера буфера
+#define UNIQUES_HASH_SET_INITIAL_SIZE_DEGREE 	4
+
+
+/** Эта хэш-функция не самая оптимальная, но состояния UniquesHashSet, посчитанные с ней,
+  *  хранятся много где на дисках (в Метраже), поэтому она продолжает использоваться.
+  */
+struct UniquesHashSetDefaultHash
+{
+	size_t operator() (UInt64 x) const
+	{
+		return intHash32<0>(x);
+	}
+};
+
+
+template <typename Hash = UniquesHashSetDefaultHash>
+class UniquesHashSet : private HashTableAllocatorWithStackMemory<(1 << UNIQUES_HASH_SET_INITIAL_SIZE_DEGREE) * sizeof(UInt32)>
+{
+private:
+	typedef UInt64 Value_t;
+	typedef UInt32 HashValue_t;
+	typedef HashTableAllocatorWithStackMemory<(1 << UNIQUES_HASH_SET_INITIAL_SIZE_DEGREE) * sizeof(UInt32)> Allocator;
+
+	UInt32 m_size;			/// Количество элементов
+	UInt8 size_degree;		/// Размер таблицы в виде степени двух
+	UInt8 skip_degree;		/// Пропускать элементы не делящиеся на 2 ^ skip_degree
+	bool has_zero;			/// Хэш-таблица содержит элемент со значением хэш-функции = 0.
+
+	HashValue_t * buf;
+
+#ifdef UNIQUES_HASH_SET_COUNT_COLLISIONS
+	/// Для профилирования.
+	mutable size_t collisions;
+#endif
+
+	void alloc(UInt8 new_size_degree)
+	{
+		buf = reinterpret_cast<HashValue_t *>(Allocator::alloc((1 << new_size_degree) * sizeof(buf[0])));
+		size_degree = new_size_degree;
+	}
+
+	void free()
+	{
+		if (buf)
+		{
+			Allocator::free(buf, buf_size() * sizeof(buf[0]));
+			buf = nullptr;
+		}
+	}
+
+	inline size_t buf_size() const						{ return 1 << size_degree; }
+	inline size_t max_fill() const						{ return 1 << (size_degree - 1); }
+	inline size_t mask() const							{ return buf_size() - 1; }
+	inline size_t place(HashValue_t x) const 			{ return (x >> UNIQUES_HASH_BITS_FOR_SKIP) & mask(); }
+
+	/// Значение делится на 2 ^ skip_degree
+	inline bool good(HashValue_t hash) const
+	{
+		return hash == ((hash >> skip_degree) << skip_degree);
+	}
+
+	HashValue_t hash(Value_t key) const
+	{
+		return Hash()(key);
+	}
+
+	/// Удалить все значения, хэши которых не делятся на 2 ^ skip_degree
+	void rehash()
+	{
+		for (size_t i = 0; i < buf_size(); ++i)
+		{
+			if (buf[i] && !good(buf[i]))
+			{
+				buf[i] = 0;
+				--m_size;
+			}
+		}
+
+		/** После удаления элементов, возможно, освободилось место для элементов,
+		  * которые были помещены дальше, чем нужно, из-за коллизии.
+		  * Надо переместить их.
+		  */
+		for (size_t i = 0; i < buf_size(); ++i)
+		{
+			if (unlikely(buf[i] && i != place(buf[i])))
+			{
+				HashValue_t x = buf[i];
+				buf[i] = 0;
+				reinsertImpl(x);
+			}
+		}
+	}
+
+	/// Увеличить размер буфера в 2 раза или до new_size_degree, если указана ненулевая.
+	void resize(size_t new_size_degree = 0)
+	{
+		size_t old_size = buf_size();
+
+		if (!new_size_degree)
+			new_size_degree = size_degree + 1;
+
+		/// Расширим пространство.
+		buf = reinterpret_cast<HashValue_t *>(Allocator::realloc(buf, old_size * sizeof(buf[0]), (1 << new_size_degree) * sizeof(buf[0])));
+		size_degree = new_size_degree;
+
+		/** Теперь некоторые элементы может потребоваться переместить на новое место.
+		  * Элемент может остаться на месте, или переместиться в новое место "справа",
+		  *  или переместиться левее по цепочке разрешения коллизий, из-за того, что элементы левее него были перемещены в новое место "справа".
+		  * Также имеется особый случай:
+		  *    если элемент должен был быть в конце старого буфера,                    [        x]
+		  *    но находится в начале из-за цепочки разрешения коллизий,                [o       x]
+		  *    то после ресайза, он сначала снова окажется не на своём месте,          [        xo        ]
+		  *    и для того, чтобы перенести его куда надо,
+		  *    надо будет после переноса всех элементов из старой половинки            [         o   x    ]
+		  *    обработать ещё хвостик из цепочки разрешения коллизий сразу после неё   [        o    x    ]
+		  * Именно для этого написано || buf[i] ниже.
+		  */
+		for (size_t i = 0; i < old_size || buf[i]; ++i)
+		{
+			HashValue_t x = buf[i];
+			if (!x)
+				continue;
+
+			size_t place_value = place(x);
+
+			/// Элемент на своём месте.
+			if (place_value == i)
+				continue;
+
+			while (buf[place_value] && buf[place_value] != x)
+			{
+				++place_value;
+				place_value &= mask();
+
+#ifdef UNIQUES_HASH_SET_COUNT_COLLISIONS
+				++collisions;
+#endif
+			}
+
+			/// Элемент остался на своём месте.
+			if (buf[place_value] == x)
+				continue;
+
+			buf[place_value] = x;
+			buf[i] = 0;
+		}
+	}
+
+	/// Вставить значение.
+	void insertImpl(HashValue_t x)
+	{
+		if (x == 0)
+		{
+			m_size += !has_zero;
+			has_zero = true;
+			return;
+		}
+
+		size_t place_value = place(x);
+		while (buf[place_value] && buf[place_value] != x)
+		{
+			++place_value;
+			place_value &= mask();
+
+#ifdef UNIQUES_HASH_SET_COUNT_COLLISIONS
+			++collisions;
+#endif
+		}
+
+		if (buf[place_value] == x)
+			return;
+
+		buf[place_value] = x;
+		++m_size;
+	}
+
+	/** Вставить в новый буфер значение, которое было в старом буфере.
+	  * Используется при увеличении размера буфера, а также при чтении из файла.
+	  */
+	void reinsertImpl(HashValue_t x)
+	{
+		size_t place_value = place(x);
+		while (buf[place_value])
+		{
+			++place_value;
+			place_value &= mask();
+
+#ifdef UNIQUES_HASH_SET_COUNT_COLLISIONS
+			++collisions;
+#endif
+		}
+
+		buf[place_value] = x;
+	}
+
+	/** Если хэш-таблица достаточно заполнена, то сделать resize.
+	  * Если элементов слишком много - то выкидывать половину, пока их не станет достаточно мало.
+	  */
+	void shrinkIfNeed()
+	{
+		if (unlikely(m_size > max_fill()))
+		{
+			if (m_size > UNIQUES_HASH_MAX_SIZE)
+			{
+				while (m_size > UNIQUES_HASH_MAX_SIZE)
+				{
+					++skip_degree;
+					rehash();
+				}
+			}
+			else
+				resize();
+		}
+	}
+
+
+public:
+	UniquesHashSet() :
+		m_size(0),
+		skip_degree(0),
+		has_zero(false)
+	{
+		alloc(UNIQUES_HASH_SET_INITIAL_SIZE_DEGREE);
+#ifdef UNIQUES_HASH_SET_COUNT_COLLISIONS
+		collisions = 0;
+#endif
+	}
+
+	UniquesHashSet(const UniquesHashSet & rhs)
+		: m_size(rhs.m_size), skip_degree(rhs.skip_degree), has_zero(rhs.has_zero)
+	{
+		alloc(rhs.size_degree);
+		memcpy(buf, rhs.buf, buf_size() * sizeof(buf[0]));
+	}
+
+	UniquesHashSet & operator= (const UniquesHashSet & rhs)
+	{
+		if (size_degree != rhs.size_degree)
+		{
+			free();
+			alloc(rhs.size_degree);
+		}
+
+		m_size = rhs.m_size;
+		skip_degree = rhs.skip_degree;
+		has_zero = rhs.has_zero;
+
+		memcpy(buf, rhs.buf, buf_size() * sizeof(buf[0]));
+
+		return *this;
+	}
+
+	~UniquesHashSet()
+	{
+		free();
+	}
+
+	void insert(Value_t x)
+	{
+		HashValue_t hash_value = hash(x);
+		if (!good(hash_value))
+			return;
+
+		insertImpl(hash_value);
+		shrinkIfNeed();
+	}
+
+	size_t size() const
+	{
+		if (0 == skip_degree)
+			return m_size;
+
+		size_t res = m_size * (1 << skip_degree);
+
+		/** Псевдослучайный остаток - для того, чтобы не было видно,
+		  * что количество делится на степень двух.
+		  */
+		res += (intHashCRC32(m_size) & ((1 << skip_degree) - 1));
+
+		/** Коррекция систематической погрешности из-за коллизий при хэшировании в UInt32.
+		  * Формула fixed_res(res)
+		  * - при каком количестве разных элементов fixed_res,
+		  *   при их случайном разбрасывании по 2^32 корзинам,
+		  *   получается в среднем res заполненных корзин.
+		  */
+		size_t p32 = 1ULL << 32;
+		size_t fixed_res = round(p32 * (log(p32) - log(p32 - res)));
+		return fixed_res;
+	}
+
+	void merge(const UniquesHashSet & rhs)
+	{
+		if (rhs.skip_degree > skip_degree)
+		{
+			skip_degree = rhs.skip_degree;
+			rehash();
+		}
+
+		if (!has_zero && rhs.has_zero)
+		{
+			has_zero = true;
+			++m_size;
+			shrinkIfNeed();
+		}
+
+		for (size_t i = 0; i < rhs.buf_size(); ++i)
+		{
+			if (rhs.buf[i] && good(rhs.buf[i]))
+			{
+				insertImpl(rhs.buf[i]);
+				shrinkIfNeed();
+			}
+		}
+	}
+
+	void write(DB::WriteBuffer & wb) const
+	{
+		if (m_size > UNIQUES_HASH_MAX_SIZE)
+			throw Poco::Exception("Cannot write UniquesHashSet: too large size_degree.");
+
+		DB::writeIntBinary(skip_degree, wb);
+		DB::writeVarUInt(m_size, wb);
+
+		if (has_zero)
+		{
+			HashValue_t x = 0;
+			DB::writeIntBinary(x, wb);
+		}
+
+		for (size_t i = 0; i < buf_size(); ++i)
+			if (buf[i])
+				DB::writeIntBinary(buf[i], wb);
+	}
+
+	void read(DB::ReadBuffer & rb)
+	{
+		has_zero = false;
+
+		DB::readIntBinary(skip_degree, rb);
+		DB::readVarUInt(m_size, rb);
+
+		if (m_size > UNIQUES_HASH_MAX_SIZE)
+			throw Poco::Exception("Cannot read UniquesHashSet: too large size_degree.");
+
+		free();
+
+		UInt8 new_size_degree = m_size <= 1
+			 ? UNIQUES_HASH_SET_INITIAL_SIZE_DEGREE
+			 : std::max(UNIQUES_HASH_SET_INITIAL_SIZE_DEGREE, static_cast<int>(log2(m_size - 1)) + 2);
+
+		alloc(new_size_degree);
+
+		for (size_t i = 0; i < m_size; ++i)
+		{
+			HashValue_t x = 0;
+			DB::readIntBinary(x, rb);
+			if (x == 0)
+				has_zero = true;
+			else
+				reinsertImpl(x);
+		}
+	}
+
+	void readAndMerge(DB::ReadBuffer & rb)
+	{
+		UInt8 rhs_skip_degree = 0;
+		DB::readIntBinary(rhs_skip_degree, rb);
+
+		if (rhs_skip_degree > skip_degree)
+		{
+			skip_degree = rhs_skip_degree;
+			rehash();
+		}
+
+		size_t rhs_size = 0;
+		DB::readVarUInt(rhs_size, rb);
+
+		if (rhs_size > UNIQUES_HASH_MAX_SIZE)
+			throw Poco::Exception("Cannot read UniquesHashSet: too large size_degree.");
+
+		if ((1U << size_degree) < rhs_size)
+		{
+			UInt8 new_size_degree = std::max(UNIQUES_HASH_SET_INITIAL_SIZE_DEGREE, static_cast<int>(log2(rhs_size - 1)) + 2);
+			resize(new_size_degree);
+		}
+
+		for (size_t i = 0; i < rhs_size; ++i)
+		{
+			HashValue_t x = 0;
+			DB::readIntBinary(x, rb);
+			insertHash(x);
+		}
+	}
+
+	static void skip(DB::ReadBuffer & rb)
+	{
+		size_t size = 0;
+
+		rb.ignore();
+		DB::readVarUInt(size, rb);
+
+		if (size > UNIQUES_HASH_MAX_SIZE)
+			throw Poco::Exception("Cannot read UniquesHashSet: too large size_degree.");
+
+		rb.ignore(sizeof(HashValue_t) * size);
+	}
+
+	void writeText(DB::WriteBuffer & wb) const
+	{
+		if (m_size > UNIQUES_HASH_MAX_SIZE)
+			throw Poco::Exception("Cannot write UniquesHashSet: too large size_degree.");
+
+		DB::writeIntText(skip_degree, wb);
+		wb.write(",", 1);
+		DB::writeIntText(m_size, wb);
+
+		if (has_zero)
+			wb.write(",0", 2);
+
+		for (size_t i = 0; i < buf_size(); ++i)
+		{
+			if (buf[i])
+			{
+				wb.write(",", 1);
+				DB::writeIntText(buf[i], wb);
+			}
+		}
+	}
+
+	void readText(DB::ReadBuffer & rb)
+	{
+		has_zero = false;
+
+		DB::readIntText(skip_degree, rb);
+		DB::assertString(",", rb);
+		DB::readIntText(m_size, rb);
+
+		if (m_size > UNIQUES_HASH_MAX_SIZE)
+			throw Poco::Exception("Cannot read UniquesHashSet: too large size_degree.");
+
+		free();
+
+		UInt8 new_size_degree = m_size <= 1
+			 ? UNIQUES_HASH_SET_INITIAL_SIZE_DEGREE
+			 : std::max(UNIQUES_HASH_SET_INITIAL_SIZE_DEGREE, static_cast<int>(log2(m_size - 1)) + 2);
+
+		alloc(new_size_degree);
+
+		for (size_t i = 0; i < m_size; ++i)
+		{
+			HashValue_t x = 0;
+			DB::assertString(",", rb);
+			DB::readIntText(x, rb);
+			if (x == 0)
+				has_zero = true;
+			else
+				reinsertImpl(x);
+		}
+	}
+
+	void insertHash(HashValue_t hash_value)
+	{
+		if (!good(hash_value))
+			return;
+
+		insertImpl(hash_value);
+		shrinkIfNeed();
+	}
+
+#ifdef UNIQUES_HASH_SET_COUNT_COLLISIONS
+	size_t getCollisions() const
+	{
+		return collisions;
+	}
+#endif
+};
+
+
+#undef UNIQUES_HASH_MAX_SIZE_DEGREE
+#undef UNIQUES_HASH_MAX_SIZE
+#undef UNIQUES_HASH_BITS_FOR_SKIP
+#undef UNIQUES_HASH_SET_INITIAL_SIZE_DEGREE

dbms/include/DB/Client/Connection.h

@@ -26,8 +26,6 @@ namespace DB
 
 using Poco::SharedPtr;
 
-class ParallelReplicas;
-
 /// Поток блоков читающих из таблицы и ее имя
 typedef std::pair<BlockInputStreamPtr, std::string> ExternalTableData;
 /// Вектор пар, описывающих таблицы
@@ -44,6 +42,7 @@ typedef std::vector<ExternalTableData> ExternalTablesData;
 class Connection : private boost::noncopyable
 {
 	friend class ParallelReplicas;
+	friend class MultiplexedConnections;
 
 public:
 	Connection(const String & host_, UInt16 port_, const String & default_database_,

dbms/include/DB/Client/ConnectionPool.h

@@ -57,7 +57,7 @@ protected:
 
 typedef SharedPtr<IConnectionPool> ConnectionPoolPtr;
 typedef std::vector<ConnectionPoolPtr> ConnectionPools;
-
+typedef SharedPtr<ConnectionPools> ConnectionPoolsPtr;
 
 
 /** Обычный пул соединений, без отказоустойчивости.

dbms/include/DB/Client/MultiplexedConnections.h

@@ -6,30 +6,38 @@
 #include <Poco/ScopedLock.h>
 #include <Poco/Mutex.h>
 
-
 namespace DB
 {
 
 
-/** Для получения данных сразу из нескольких реплик (соединений) в рамках одного потока.
-  * В качестве вырожденного случая, может также работать с одним соединением.
+/** Для получения данных сразу из нескольких реплик (соединений) из одного или нексольких шардов
+  * в рамках одного потока. В качестве вырожденного случая, может также работать с одним соединением.
   * Предполагается, что все функции кроме sendCancel всегда выполняются в одном потоке.
   *
   * Интерфейс почти совпадает с Connection.
   */
-class ParallelReplicas final : private boost::noncopyable
+class MultiplexedConnections final : private boost::noncopyable
 {
 public:
 	/// Принимает готовое соединение.
-	ParallelReplicas(Connection * connection_, const Settings * settings_, ThrottlerPtr throttler_);
+	MultiplexedConnections(Connection * connection_, const Settings * settings_, ThrottlerPtr throttler_);
 
 	/** Принимает пул, из которого нужно будет достать одно или несколько соединений.
 	  * Если флаг append_extra_info установлен, к каждому полученному блоку прилагается
 	  * дополнительная информация.
 	  * Если флаг get_all_replicas установлен, достаются все соединения.
 	  */
-	ParallelReplicas(IConnectionPool * pool_, const Settings * settings_, ThrottlerPtr throttler_,
-		bool append_extra_info = false, bool get_all_replicas = false);
+	MultiplexedConnections(IConnectionPool * pool_, const Settings * settings_, ThrottlerPtr throttler_,
+		bool append_extra_info = false, bool do_broadcast = false);
+
+	/** Принимает пулы, один для каждого шарда, из которих нужно будет достать одно или несколько
+	  * соединений.
+	  * Если флаг append_extra_info установлен, к каждому полученному блоку прилагается
+	  * дополнительная информация.
+	  * Если флаг do_broadcast установлен, достаются все соединения.
+	  */
+	MultiplexedConnections(ConnectionPools & pools_, const Settings * settings_, ThrottlerPtr throttler_,
+		bool append_extra_info = false, bool do_broadcast = false);
 
 	/// Отправить на реплики всё содержимое внешних таблиц.
 	void sendExternalTablesData(std::vector<ExternalTablesData> & data);
@@ -65,15 +73,44 @@ public:
 
 	/// Проверить, есть ли действительные реплики.
 	/// Без блокировки, потому что sendCancel() не меняет состояние реплик.
-	bool hasActiveReplicas() const { return active_replica_count > 0; }
+	bool hasActiveConnections() const { return active_connection_total_count > 0; }
 
 private:
-	/// Реплики хэшированные по id сокета
-	using ReplicaMap = std::unordered_map<int, Connection *>;
+	/// Соединения 1-го шарда, затем соединения 2-го шарда, и т.д.
+	using Connections = std::vector<Connection *>;
+
+	/// Состояние соединений одного шарда.
+	struct ShardState
+	{
+		/// Количество выделенных соединений, т.е. реплик, для этого шарда.
+		size_t allocated_connection_count;
+		/// Текущее количество действительных соединений к репликам этого шарда.
+		size_t active_connection_count;
+	};
+
+	/// Описание одной реплики.
+	struct ReplicaState
+	{
+		/// Индекс соединения.
+		size_t connection_index;
+		/// Владелец этой реплики.
+		ShardState * shard_state;
+	};
+
+	/// Реплики хэшированные по id сокета.
+	using ReplicaMap = std::unordered_map<int, ReplicaState>;
+
+	/// Состояние каждого шарда.
+	using ShardStates = std::vector<ShardState>;
 
 private:
-	/// Зарегистрировать реплику.
-	void registerReplica(Connection * connection);
+	void initFromShard(IConnectionPool * pool);
+
+	/// Зарегистрировать шарды.
+	void registerShards();
+
+	/// Зарегистрировать реплики одного шарда.
+	void registerReplicas(size_t index_begin, size_t index_end, ShardState & shard_state);
 
 	/// Внутренняя версия функции receivePacket без блокировки.
 	Connection::Packet receivePacketUnlocked();
@@ -94,13 +131,15 @@ private:
 
 private:
 	const Settings * settings;
+
+	Connections connections;
 	ReplicaMap replica_map;
+	ShardStates shard_states;
 
 	/// Если не nullptr, то используется, чтобы ограничить сетевой трафик.
 	ThrottlerPtr throttler;
 
 	std::vector<ConnectionPool::Entry> pool_entries;
-	ConnectionPool::Entry pool_entry;
 
 	/// Соединение, c которого был получен последний блок.
 	Connection * current_connection;
@@ -108,7 +147,7 @@ private:
 	std::unique_ptr<BlockExtraInfo> block_extra_info;
 
 	/// Текущее количество действительных соединений к репликам.
-	size_t active_replica_count;
+	size_t active_connection_total_count = 0;
 	/// Запрос выполняется параллельно на нескольких репликах.
 	bool supports_parallel_execution;
 	/// Отправили запрос
@@ -116,6 +155,8 @@ private:
 	/// Отменили запрос
 	bool cancelled = false;
 
+	bool do_broadcast = false;
+
 	/// Мьютекс для того, чтобы функция sendCancel могла выполняться безопасно
 	/// в отдельном потоке.
 	mutable Poco::FastMutex cancel_mutex;

dbms/include/DB/Columns/ColumnAggregateFunction.h

@@ -103,18 +103,9 @@ public:
 		arenas.push_back(arena_);
 	}
 
-	ColumnPtr convertToValues() const
-	{
-		const IAggregateFunction * function = holder->func;
-		ColumnPtr res = function->getReturnType()->createColumn();
-		IColumn & column = *res;
-		res->reserve(getData().size());
-
-		for (auto val : getData())
-			function->insertResultInto(val, column);
-
-		return res;
-	}
+	/** Преобразовать столбец состояний агрегатной функции в столбец с готовыми значениями результатов.
+	  */
+	ColumnPtr convertToValues() const;
 
 	std::string getName() const override { return "ColumnAggregateFunction"; }
 
@@ -174,6 +165,9 @@ public:
 	{
 		IAggregateFunction * function = holder.get()->func;
 
+		if (unlikely(arenas.empty()))
+			arenas.emplace_back(new Arena);
+
 		getData().push_back(arenas.back().get()->alloc(function->sizeOfData()));
 		function->create(getData().back());
 		ReadBufferFromString read_buffer(x.get<const String &>());

dbms/include/DB/Columns/ColumnArray.h

@@ -266,6 +266,25 @@ public:
 
 	ColumnPtr replicate(const Offsets_t & replicate_offsets) const override;
 
+
+	ColumnPtr convertToFullColumnIfConst() const override
+	{
+		ColumnPtr new_data;
+		ColumnPtr new_offsets;
+
+		if (auto full_column = data->convertToFullColumnIfConst())
+			new_data = full_column;
+		else
+			new_data = data;
+
+		if (auto full_column = offsets->convertToFullColumnIfConst())
+			new_offsets = full_column;
+		else
+			new_offsets = offsets;
+
+		return new ColumnArray(new_data, new_offsets);
+	}
+
 private:
 	ColumnPtr data;
 	ColumnPtr offsets;	/// Смещения могут быть разделяемыми для нескольких столбцов - для реализации вложенных структур данных.

dbms/include/DB/Columns/ColumnConst.h

@@ -21,6 +21,7 @@ class IColumnConst : public IColumn
 public:
 	bool isConst() const override { return true; }
 	virtual ColumnPtr convertToFullColumn() const = 0;
+	ColumnPtr convertToFullColumnIfConst() const override { return convertToFullColumn(); }
 };
 
 

dbms/include/DB/Columns/ColumnSet.h

@@ -14,7 +14,7 @@ namespace DB
 class ColumnSet final : public IColumnDummy
 {
 public:
-	ColumnSet(size_t s_, SetPtr data_) : IColumnDummy(s_), data(data_) {}
+	ColumnSet(size_t s_, ConstSetPtr data_) : IColumnDummy(s_), data(data_) {}
 
 	/// Столбец не константный. Иначе столбец будет использоваться в вычислениях в ExpressionActions::prepare, когда множество из подзапроса ещё не готово.
 	bool isConst() const override { return false; }
@@ -22,11 +22,10 @@ public:
 	std::string getName() const override { return "ColumnSet"; }
 	ColumnPtr cloneDummy(size_t s_) const override { return new ColumnSet(s_, data); }
 
-	SetPtr & getData() { return data; }
-	const SetPtr & getData() const { return data; }
+	ConstSetPtr getData() const { return data; }
 
 private:
-	SetPtr data;
+	ConstSetPtr data;
 };
 
 }

dbms/include/DB/Columns/ColumnTuple.h

@@ -242,9 +242,22 @@ public:
 			columns[i]->getExtremes(min.get<Array &>()[i], max.get<Array &>()[i]);
 	}
 
+	ColumnPtr convertToFullColumnIfConst() const override
+	{
+		Block materialized = data;
+		for (size_t i = 0, size = materialized.columns(); i < size; ++i)
+			if (auto converted = materialized.unsafeGetByPosition(i).column->convertToFullColumnIfConst())
+				materialized.unsafeGetByPosition(i).column = converted;
+
+		return new ColumnTuple(materialized);
+	}
+
 
 	const Block & getData() const { return data; }
 	Block & getData() { return data; }
+
+	const Columns & getColumns() const { return columns; }
+	Columns & getColumns() { return columns; }
 };
 
 

dbms/include/DB/Columns/IColumn.h

@@ -42,6 +42,15 @@ public:
 	  */
 	virtual bool isConst() const { return false; }
 
+	/** Если столбец не константа - возвращает nullptr (либо может вернуть самого себя).
+	  * Если столбец константа, то превращает его в полноценный столбец (если тип столбца предполагает такую возможность) и возвращает его.
+	  * Отдельный случай:
+	  * Если столбец состоит из нескольких других столбцов (пример: кортеж),
+	  *  и он может содержать как константные, так и полноценные столбцы,
+	  *  то превратить в нём все константные столбцы в полноценные, и вернуть результат.
+	  */
+	virtual SharedPtr<IColumn> convertToFullColumnIfConst() const { return {}; }
+
 	/** Значения имеют фиксированную длину.
 	  */
 	virtual bool isFixed() const { return false; }

dbms/include/DB/Common/AIO.h

@@ -1,19 +1,26 @@
 #pragma once
 
-#include <linux/aio_abi.h>
-#include <unistd.h>
-#include <sys/syscall.h>
-
-#include <boost/noncopyable.hpp>
-
+#include <DB/Core/ErrorCodes.h>
 #include <DB/Common/Exception.h>
+#include <common/logger_useful.h>
+#include <common/singleton.h>
+#include <Poco/Logger.h>
+#include <boost/range/iterator_range.hpp>
+#include <boost/noncopyable.hpp>
+#include <condition_variable>
+#include <future>
+#include <mutex>
+#include <map>
+#include <linux/aio_abi.h>
+#include <sys/syscall.h>
+#include <unistd.h>
 
 
 /** Небольшие обёртки для асинхронного ввода-вывода.
   */
 
 
-inline int io_setup(unsigned nr, aio_context_t *ctxp)
+inline int io_setup(unsigned nr, aio_context_t * ctxp)
 {
 	return syscall(__NR_io_setup, nr, ctxp);
 }
@@ -23,12 +30,13 @@ inline int io_destroy(aio_context_t ctx)
 	return syscall(__NR_io_destroy, ctx);
 }
 
-inline int io_submit(aio_context_t ctx, long nr,  struct iocb **iocbpp)
+/// last argument is an array of pointers technically speaking
+inline int io_submit(aio_context_t ctx, long nr, struct iocb * iocbpp[])
 {
 	return syscall(__NR_io_submit, ctx, nr, iocbpp);
 }
 
-inline int io_getevents(aio_context_t ctx, long min_nr, long max_nr, io_event *events, struct timespec *timeout)
+inline int io_getevents(aio_context_t ctx, long min_nr, long max_nr, io_event *events, struct timespec * timeout)
 {
 	return syscall(__NR_io_getevents, ctx, min_nr, max_nr, events, timeout);
 }
@@ -50,3 +58,159 @@ struct AIOContext : private boost::noncopyable
 		io_destroy(ctx);
 	}
 };
+
+namespace DB
+{
+
+
+class AIOContextPool : public Singleton<AIOContextPool>
+{
+	friend class Singleton<AIOContextPool>;
+
+	static const auto max_concurrent_events = 128;
+	static const auto timeout_sec = 1;
+
+	AIOContext aio_context{max_concurrent_events};
+
+	using id_t = size_t;
+	using bytes_read_t = ssize_t;
+
+	/// Autoincremental id used to identify completed requests
+	id_t id{};
+	mutable std::mutex mutex;
+	mutable std::condition_variable have_resources;
+	std::map<id_t, std::promise<bytes_read_t>> promises;
+
+	std::atomic<bool> cancelled{false};
+	std::thread io_completion_monitor{&AIOContextPool::doMonitor, this};
+
+	~AIOContextPool()
+	{
+		cancelled.store(true, std::memory_order_relaxed);
+		io_completion_monitor.join();
+	}
+
+	void doMonitor()
+	{
+		/// continue checking for events unless cancelled
+		while (!cancelled.load(std::memory_order_relaxed))
+			waitForCompletion();
+
+		/// wait until all requests have been completed
+		while (!promises.empty())
+			waitForCompletion();
+	}
+
+	void waitForCompletion()
+	{
+		/// array to hold completion events
+		io_event events[max_concurrent_events];
+
+		try
+		{
+			const auto num_events = getCompletionEvents(events, max_concurrent_events);
+			fulfillPromises(events, num_events);
+			notifyProducers(num_events);
+		}
+		catch (...)
+		{
+			/// there was an error, log it, return to any producer and continue
+			reportExceptionToAnyProducer();
+			tryLogCurrentException("AIOContextPool::waitForCompletion()");
+		}
+	}
+
+	int getCompletionEvents(io_event events[], const int max_events)
+	{
+		timespec timeout{timeout_sec};
+
+		auto num_events = 0;
+
+		/// request 1 to `max_events` events
+		while ((num_events = io_getevents(aio_context.ctx, 1, max_events, events, &timeout)) < 0)
+			if (errno != EINTR)
+				throwFromErrno("io_getevents: Failed to wait for asynchronous IO completion",
+					ErrorCodes::AIO_COMPLETION_ERROR, errno);
+
+		return num_events;
+	}
+
+	void fulfillPromises(const io_event events[], const int num_events)
+	{
+		if (num_events == 0)
+			return;
+
+		const std::lock_guard<std::mutex> lock{mutex};
+
+		/// look at returned events and find corresponding promise, set result and erase promise from map
+		for (const auto & event : boost::make_iterator_range(events, events + num_events))
+		{
+			/// get id from event
+			const auto id = event.data;
+
+			/// set value via promise and release it
+			const auto it = promises.find(id);
+			if (it == std::end(promises))
+			{
+				LOG_CRITICAL(&Poco::Logger::get("AIOcontextPool"), "Found io_event with unknown id " << id);
+				continue;
+			}
+
+			it->second.set_value(event.res);
+			promises.erase(it);
+		}
+	}
+
+	void notifyProducers(const int num_producers) const
+	{
+		if (num_producers == 0)
+			return;
+
+		if (num_producers > 1)
+			have_resources.notify_all();
+		else
+			have_resources.notify_one();
+	}
+
+	void reportExceptionToAnyProducer()
+	{
+		const std::lock_guard<std::mutex> lock{mutex};
+
+		const auto any_promise_it = std::begin(promises);
+		any_promise_it->second.set_exception(std::current_exception());
+	}
+
+public:
+	/// Request AIO read operation for iocb, returns a future with number of bytes read
+	std::future<bytes_read_t> post(struct iocb & iocb)
+	{
+		std::unique_lock<std::mutex> lock{mutex};
+
+		/// get current id and increment it by one
+		const auto request_id = id++;
+
+		/// create a promise and put request in "queue"
+		promises.emplace(request_id, std::promise<bytes_read_t>{});
+		/// store id in AIO request for further identification
+		iocb.aio_data = request_id;
+
+		auto num_requests = 0;
+		struct iocb * requests[] { &iocb };
+
+		/// submit a request
+		while ((num_requests = io_submit(aio_context.ctx, 1, requests)) < 0)
+		{
+			if (errno == EAGAIN)
+				/// wait until at least one event has been completed (or a spurious wakeup) and try again
+				have_resources.wait(lock);
+			else if (errno != EINTR)
+				throwFromErrno("io_submit: Failed to submit a request for asynchronous IO",
+					ErrorCodes::AIO_SUBMIT_ERROR, errno);
+		}
+
+		return promises[request_id].get_future();
+	}
+};
+
+
+}

dbms/include/DB/Common/Allocator.h

@@ -9,19 +9,42 @@
 #include <DB/Core/ErrorCodes.h>
 
 
+/** При использовании AllocatorWithStackMemory, размещённом на стеке,
+  *  GCC 4.9 ошибочно делает предположение, что мы можем вызывать free от указателя на стек.
+  * На самом деле, комбинация условий внутри AllocatorWithStackMemory этого не допускает.
+  */
+#if !__clang__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wfree-nonheap-object"
+#endif
+
+
 /** Отвечает за выделение/освобождение памяти. Используется, например, в PODArray, Arena.
+  * Также используется в хэш-таблицах.
   * Интерфейс отличается от std::allocator
   * - наличием метода realloc, который для больших кусков памяти использует mremap;
   * - передачей размера в метод free;
   * - наличием аргумента alignment;
+  * - возможностью зануления памяти (используется в хэш-таблицах);
   */
+template <bool clear_memory_>
 class Allocator
 {
+protected:
+	static constexpr bool clear_memory = clear_memory_;
+
 private:
-	/** См. комментарий в HashTableAllocator.h
+	/** Многие современные аллокаторы (например, tcmalloc) не умеют делать mremap для realloc,
+	  *  даже в случае достаточно больших кусков памяти.
+	  * Хотя это позволяет увеличить производительность и уменьшить потребление памяти во время realloc-а.
+	  * Чтобы это исправить, делаем mremap самостоятельно, если кусок памяти достаточно большой.
+	  * Порог (64 МБ) выбран достаточно большим, так как изменение адресного пространства
+	  *  довольно сильно тормозит, особенно в случае наличия большого количества потоков.
+	  * Рассчитываем, что набор операций mmap/что-то сделать/mremap может выполняться всего лишь около 1000 раз в секунду.
+	  *
+	  * PS. Также это требуется, потому что tcmalloc не может выделить кусок памяти больше 16 GB.
 	  */
 	static constexpr size_t MMAP_THRESHOLD = 64 * (1 << 20);
-	static constexpr size_t HUGE_PAGE_SIZE = 2 * (1 << 20);
 	static constexpr size_t MMAP_MIN_ALIGNMENT = 4096;
 	static constexpr size_t MALLOC_MIN_ALIGNMENT = 8;
 
@@ -43,14 +66,15 @@ public:
 			if (MAP_FAILED == buf)
 				DB::throwFromErrno("Allocator: Cannot mmap.", DB::ErrorCodes::CANNOT_ALLOCATE_MEMORY);
 
-			/// См. комментарий в HashTableAllocator.h
-			if (size >= HUGE_PAGE_SIZE && 0 != madvise(buf, size, MADV_HUGEPAGE))
-				DB::throwFromErrno("HashTableAllocator: Cannot madvise with MADV_HUGEPAGE.", DB::ErrorCodes::CANNOT_ALLOCATE_MEMORY);
+			/// Заполнение нулями не нужно - mmap сам это делает.
 		}
 		else
 		{
 			if (alignment <= MALLOC_MIN_ALIGNMENT)
 			{
+				if (clear_memory)
+					buf = ::calloc(size, 1);
+				else
 					buf = ::malloc(size);
 
 				if (nullptr == buf)
@@ -63,6 +87,9 @@ public:
 
 				if (0 != res)
 					DB::throwFromErrno("Cannot allocate memory (posix_memalign)", DB::ErrorCodes::CANNOT_ALLOCATE_MEMORY, res);
+
+				if (clear_memory)
+					memset(buf, 0, size);
 			}
 		}
 
@@ -101,6 +128,9 @@ public:
 
 			if (nullptr == buf)
 				DB::throwFromErrno("Allocator: Cannot realloc.", DB::ErrorCodes::CANNOT_ALLOCATE_MEMORY);
+
+			if (clear_memory)
+				memset(reinterpret_cast<char *>(buf) + old_size, 0, new_size - old_size);
 		}
 		else if (old_size >= MMAP_THRESHOLD && new_size >= MMAP_THRESHOLD)
 		{
@@ -110,6 +140,8 @@ public:
 			buf = mremap(buf, old_size, new_size, MREMAP_MAYMOVE);
 			if (MAP_FAILED == buf)
 				DB::throwFromErrno("Allocator: Cannot mremap.", DB::ErrorCodes::CANNOT_MREMAP);
+
+			/// Заполнение нулями не нужно.
 		}
 		else
 		{
@@ -122,3 +154,53 @@ public:
 		return buf;
 	}
 };
+
+
+/** Аллокатор с оптимизацией для маленьких кусков памяти.
+  */
+template <typename Base, size_t N = 64>
+class AllocatorWithStackMemory : private Base
+{
+private:
+	char stack_memory[N];
+
+public:
+	void * alloc(size_t size)
+	{
+		if (size <= N)
+		{
+			if (Base::clear_memory)
+				memset(stack_memory, 0, N);
+			return stack_memory;
+		}
+
+		return Base::alloc(size);
+	}
+
+	void free(void * buf, size_t size)
+	{
+		if (size > N)
+			Base::free(buf, size);
+	}
+
+	void * realloc(void * buf, size_t old_size, size_t new_size)
+	{
+		/// Было в stack_memory, там и останется.
+		if (new_size <= N)
+			return buf;
+
+		/// Уже не помещалось в stack_memory.
+		if (old_size > N)
+			return Base::realloc(buf, old_size, new_size);
+
+		/// Было в stack_memory, но теперь не помещается.
+		void * new_buf = Base::alloc(new_size);
+		memcpy(new_buf, buf, old_size);
+		return new_buf;
+	}
+};
+
+
+#if !__clang__
+#pragma GCC diagnostic pop
+#endif

dbms/include/DB/Common/Arena.h

@@ -26,7 +26,7 @@ class Arena
 {
 private:
 	/// Непрерывный кусок памяти и указатель на свободное место в нём. Односвязный список.
-	struct Chunk : private Allocator	/// empty base optimization
+	struct Chunk : private Allocator<false>	/// empty base optimization
 	{
 		char * begin;
 		char * pos;

dbms/include/DB/Common/ArenaWithFreeLists.h

@@ -0,0 +1,93 @@
+#pragma once
+
+#include <DB/Common/Arena.h>
+#include <ext/size.hpp>
+#include <cstdlib>
+#include <memory>
+#include <array>
+
+
+namespace DB
+{
+
+
+class ArenaWithFreeLists : private Allocator<false>
+{
+private:
+	struct Block { Block * next; };
+
+	static const std::array<std::size_t, 14> & getSizes()
+	{
+		static constexpr std::array<std::size_t, 14> sizes{
+			8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536
+		};
+
+		static_assert(sizes.front() >= sizeof(Block), "Can't make allocations smaller than sizeof(Block)");
+
+		return sizes;
+	}
+
+	static auto getMinBucketNum() { return 3; }
+	static auto getMaxFixedBlockSize() { return getSizes().back(); }
+
+	Arena pool;
+	const std::unique_ptr<Block * []> free_lists = std::make_unique<Block * []>(ext::size(getSizes()));
+
+	static std::size_t findFreeListIndex(const std::size_t size)
+	{
+		/// shift powers of two into previous bucket by subtracting 1
+		const auto bucket_num = _bit_scan_reverse(size - 1);
+
+		return std::max(bucket_num, getMinBucketNum()) - getMinBucketNum();
+	}
+
+public:
+	ArenaWithFreeLists(
+		const std::size_t initial_size = 4096, const std::size_t growth_factor = 2,
+		const std::size_t linear_growth_threshold = 128 * 1024 * 1024)
+		: pool{initial_size, growth_factor, linear_growth_threshold}
+	{
+	}
+
+	char * alloc(const std::size_t size)
+	{
+		if (size > getMaxFixedBlockSize())
+			return static_cast<char *>(Allocator::alloc(size));
+
+		/// find list of required size
+		const auto list_idx = findFreeListIndex(size);
+
+		if (auto & block = free_lists[list_idx])
+		{
+			const auto res = ext::bit_cast<char *>(block);
+			block = block->next;
+			return res;
+		}
+
+		/// no block of corresponding size, allocate a new one
+		return pool.alloc(getSizes()[list_idx]);
+	}
+
+	void free(const void * ptr, const std::size_t size)
+	{
+		if (size > getMaxFixedBlockSize())
+			return Allocator::free(const_cast<void *>(ptr), size);
+
+		/// find list of required size
+		const auto list_idx = findFreeListIndex(size);
+
+		auto & block = free_lists[list_idx];
+		const auto old = block;
+		block = ext::bit_cast<Block *>(ptr);
+		block->next = old;
+	}
+
+	/// Размер выделенного пула в байтах
+	size_t size() const
+	{
+		return pool.size();
+	}
+};
+
+
+}

dbms/include/DB/Common/CompactArray.h

@@ -10,11 +10,11 @@
 namespace DB
 {
 
-/** Компактный массив для хранения данных, размер L, в битах, которых составляет
+/** Компактный массив для хранения данных, размер content_width, в битах, которых составляет
   * меньше одного байта. Вместо того, чтобы хранить каждое значение в отдельный
-  * байт, что приводит к растрате 37.5% пространства для L=5, CompactArray хранит
-  * смежные L-битные значения в массиве байтов, т.е. фактически CompactArray
-  * симулирует массив L-битных значений.
+  * байт, что приводит к растрате 37.5% пространства для content_width=5, CompactArray хранит
+  * смежные content_width-битные значения в массиве байтов, т.е. фактически CompactArray
+  * симулирует массив content_width-битных значений.
   */
 template <typename BucketIndex, UInt8 content_width, size_t bucket_count>
 class __attribute__ ((packed)) CompactArray final

dbms/include/DB/Common/HashTable/Hash.h

@@ -121,3 +121,42 @@ struct TrivialHash
 		return key;
 	}
 };
+
+
+/** Сравнительно неплохая некриптографическая хэш функция из UInt64 в UInt32.
+  * Но хуже (и по качеству и по скорости), чем просто срезка intHash64.
+  * Взята отсюда: http://www.concentric.net/~ttwang/tech/inthash.htm
+  *
+  * Немного изменена по сравнению с функцией по ссылке: сдвиги вправо случайно заменены на цикличесвие сдвиги вправо.
+  * Это изменение никак не повлияло на результаты тестов smhasher.
+  *
+  * Рекомендуется для разных задач использовать разные salt.
+  * А то был случай, что в БД значения сортировались по хэшу (для некачественного псевдослучайного разбрасывания),
+  *  а в другом месте, в агрегатной функции, в хэш таблице использовался такой же хэш,
+  *  в результате чего, эта агрегатная функция чудовищно тормозила из-за коллизий.
+  */
+template <DB::UInt64 salt>
+inline DB::UInt32 intHash32(DB::UInt64 key)
+{
+	key ^= salt;
+
+	key = (~key) + (key << 18);
+	key = key ^ ((key >> 31) | (key << 33));
+	key = key * 21;
+	key = key ^ ((key >> 11) | (key << 53));
+	key = key + (key << 6);
+	key = key ^ ((key >> 22) | (key << 42));
+
+	return key;
+}
+
+
+/// Для контейнеров.
+template <typename T, DB::UInt64 salt = 0>
+struct IntHash32
+{
+	size_t operator() (const T & key) const
+	{
+		return intHash32<salt>(key);
+	}
+};

dbms/include/DB/Common/HashTable/HashTable.h

@@ -11,8 +11,6 @@
 
 #include <common/likely.h>
 
-#include <stats/IntHash.h>
-
 #include <DB/Core/Defines.h>
 #include <DB/Core/Types.h>
 #include <DB/Common/Exception.h>

dbms/include/DB/Common/HashTable/HashTableAllocator.h

@@ -1,184 +1,9 @@
 #pragma once
 
-#include <malloc.h>
-#include <string.h>
-#include <sys/mman.h>
-
-#include <DB/Common/MemoryTracker.h>
-#include <DB/Common/Exception.h>
-#include <DB/Core/ErrorCodes.h>
-
-/** При использовании HashTableAllocatorWithStackMemory, размещённом на стеке,
-  *  GCC 4.9 ошибочно делает предположение, что мы можем вызывать free от указателя на стек.
-  * На самом деле, комбинация условий внутри HashTableAllocatorWithStackMemory этого не допускает.
-  */
-#if !__clang__
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wfree-nonheap-object"
-#endif
+#include <DB/Common/Allocator.h>
 
 
-/** Общая часть разных хэш-таблиц, отвечающая за выделение/освобождение памяти.
-  * Отличается от Allocator тем, что зануляет память.
-  * Используется в качестве параметра шаблона (есть несколько реализаций с таким же интерфейсом).
-  */
-class HashTableAllocator
-{
-private:
-	/** Многие современные аллокаторы (например, tcmalloc) не умеют делать mremap для realloc,
-	  *  даже в случае достаточно больших кусков памяти.
-	  * Хотя это позволяет увеличить производительность и уменьшить потребление памяти во время realloc-а.
-	  * Чтобы это исправить, делаем mremap самостоятельно, если кусок памяти достаточно большой.
-	  * Порог (64 МБ) выбран достаточно большим, так как изменение адресного пространства
-	  *  довольно сильно тормозит, особенно в случае наличия большого количества потоков.
-	  * Рассчитываем, что набор операций mmap/что-то сделать/mremap может выполняться всего лишь около 1000 раз в секунду.
-	  *
-	  * PS. Также это требуется, потому что tcmalloc не может выделить кусок памяти больше 16 GB.
-	  */
-	static constexpr size_t MMAP_THRESHOLD = 64 * (1 << 20);
-	static constexpr size_t HUGE_PAGE_SIZE = 2 * (1 << 20);
+using HashTableAllocator = Allocator<true>;
 
-public:
-	/// Выделить кусок памяти и заполнить его нулями.
-	void * alloc(size_t size)
-	{
-		if (current_memory_tracker)
-			current_memory_tracker->alloc(size);
-
-		void * buf;
-
-		if (size >= MMAP_THRESHOLD)
-		{
-			buf = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-			if (MAP_FAILED == buf)
-				DB::throwFromErrno("HashTableAllocator: Cannot mmap.", DB::ErrorCodes::CANNOT_ALLOCATE_MEMORY);
-
-			/** Использование huge pages позволяет увеличить производительность более чем в три раза
-			  *  в запросе SELECT number % 1000000 AS k, count() FROM system.numbers GROUP BY k,
-			  *  (хэш-таблица на 1 000 000 элементов)
-			  * и примерно на 15% в случае хэш-таблицы на 100 000 000 элементов.
-			  */
-			if (size >= HUGE_PAGE_SIZE && 0 != madvise(buf, size, MADV_HUGEPAGE))
-				DB::throwFromErrno("HashTableAllocator: Cannot madvise with MADV_HUGEPAGE.", DB::ErrorCodes::CANNOT_ALLOCATE_MEMORY);
-
-			/// Заполнение нулями не нужно - mmap сам это делает.
-		}
-		else
-		{
-			buf = ::calloc(size, 1);
-			if (nullptr == buf)
-				DB::throwFromErrno("HashTableAllocator: Cannot calloc.", DB::ErrorCodes::CANNOT_ALLOCATE_MEMORY);
-		}
-
-		return buf;
-	}
-
-	/// Освободить память.
-	void free(void * buf, size_t size)
-	{
-		if (size >= MMAP_THRESHOLD)
-		{
-			if (0 != munmap(buf, size))
-				DB::throwFromErrno("HashTableAllocator: Cannot munmap.", DB::ErrorCodes::CANNOT_MUNMAP);
-		}
-		else
-		{
-			::free(buf);
-		}
-
-		if (current_memory_tracker)
-			current_memory_tracker->free(size);
-	}
-
-	/** Увеличить размер куска памяти.
-	  * Содержимое старого куска памяти переезжает в начало нового.
-	  * Оставшаяся часть заполняется нулями.
-	  * Положение куска памяти может измениться.
-	  */
-	void * realloc(void * buf, size_t old_size, size_t new_size)
-	{
-		if (old_size < MMAP_THRESHOLD && new_size < MMAP_THRESHOLD)
-		{
-			if (current_memory_tracker)
-				current_memory_tracker->realloc(old_size, new_size);
-
-			buf = ::realloc(buf, new_size);
-			if (nullptr == buf)
-				DB::throwFromErrno("HashTableAllocator: Cannot realloc.", DB::ErrorCodes::CANNOT_ALLOCATE_MEMORY);
-
-			memset(reinterpret_cast<char *>(buf) + old_size, 0, new_size - old_size);
-		}
-		else if (old_size >= MMAP_THRESHOLD && new_size >= MMAP_THRESHOLD)
-		{
-			if (current_memory_tracker)
-				current_memory_tracker->realloc(old_size, new_size);
-
-			buf = mremap(buf, old_size, new_size, MREMAP_MAYMOVE);
-			if (MAP_FAILED == buf)
-				DB::throwFromErrno("HashTableAllocator: Cannot mremap.", DB::ErrorCodes::CANNOT_MREMAP);
-
-			/** Здесь не получается сделать madvise с MADV_HUGEPAGE.
-			  * Похоже, что при mremap, huge pages сами расширяются на новую область.
-			  */
-
-			/// Заполнение нулями не нужно.
-		}
-		else
-		{
-			void * new_buf = alloc(new_size);
-			memcpy(new_buf, buf, old_size);
-			free(buf, old_size);
-			buf = new_buf;
-		}
-
-		return buf;
-	}
-};
-
-
-/** Аллокатор с оптимизацией для маленьких кусков памяти.
-  */
 template <size_t N = 64>
-class HashTableAllocatorWithStackMemory : private HashTableAllocator
-{
-private:
-	char stack_memory[N];
-
-public:
-	void * alloc(size_t size)
-	{
-		if (size <= N)
-		{
-			memset(stack_memory, 0, N);
-			return stack_memory;
-		}
-
-		return HashTableAllocator::alloc(size);
-	}
-
-	void free(void * buf, size_t size)
-	{
-		if (size > N)
-			HashTableAllocator::free(buf, size);
-	}
-
-	void * realloc(void * buf, size_t old_size, size_t new_size)
-	{
-		/// Было в stack_memory, там и останется.
-		if (new_size <= N)
-			return buf;
-
-		/// Уже не помещалось в stack_memory.
-		if (old_size > N)
-			return HashTableAllocator::realloc(buf, old_size, new_size);
-
-		/// Было в stack_memory, но теперь не помещается.
-		void * new_buf = HashTableAllocator::alloc(new_size);
-		memcpy(new_buf, buf, old_size);
-		return new_buf;
-	}
-};
-
-#if !__clang__
-#pragma GCC diagnostic pop
-#endif
+using HashTableAllocatorWithStackMemory = AllocatorWithStackMemory<HashTableAllocator, N>;

dbms/include/DB/Common/HyperLogLogCounter.h

@@ -1,9 +1,9 @@
 #pragma once
 
 #include <common/Common.h>
-#include <stats/IntHash.h>
 #include <DB/Common/HyperLogLogBiasEstimator.h>
 #include <DB/Common/CompactArray.h>
+#include <DB/Common/HashTable/Hash.h>
 
 #include <DB/IO/ReadBuffer.h>
 #include <DB/IO/WriteBuffer.h>

dbms/include/DB/Common/OptimizedRegularExpression.inl

@@ -9,7 +9,11 @@
 #define MAX_SUBPATTERNS 5
 
 template <bool b>
-void OptimizedRegularExpressionImpl<b>::analyze(const std::string & regexp, std::string & required_substring, bool & is_trivial, bool & required_substring_is_prefix)
+void OptimizedRegularExpressionImpl<b>::analyze(
+	const std::string & regexp,
+	std::string & required_substring,
+	bool & is_trivial,
+	bool & required_substring_is_prefix)
 {
 	/** Выражение тривиально, если в нём все метасимволы эскейплены.
 	  * Безальтернативная строка - это
@@ -44,6 +48,7 @@ void OptimizedRegularExpressionImpl<b>::analyze(const std::string & regexp, std:
 			case '\0':
 				pos = end;
 				break;
+
 			case '\\':
 			{
 				++pos;
@@ -74,6 +79,7 @@ void OptimizedRegularExpressionImpl<b>::analyze(const std::string & regexp, std:
 				++pos;
 				break;
 			}
+
 			case '|':
 				if (depth == 0)
 					has_alternative_on_depth_0 = true;
@@ -85,6 +91,7 @@ void OptimizedRegularExpressionImpl<b>::analyze(const std::string & regexp, std:
 				}
 				++pos;
 				break;
+
 			case '(':
 				if (!in_square_braces)
 				{
@@ -98,6 +105,7 @@ void OptimizedRegularExpressionImpl<b>::analyze(const std::string & regexp, std:
 				}
 				++pos;
 				break;
+
 			case '[':
 				in_square_braces = true;
 				++depth;
@@ -109,7 +117,11 @@ void OptimizedRegularExpressionImpl<b>::analyze(const std::string & regexp, std:
 				}
 				++pos;
 				break;
+
 			case ']':
+				if (!in_square_braces)
+					goto ordinary;
+
 				in_square_braces = false;
 				--depth;
 				is_trivial = false;
@@ -120,6 +132,7 @@ void OptimizedRegularExpressionImpl<b>::analyze(const std::string & regexp, std:
 				}
 				++pos;
 				break;
+
 			case ')':
 				if (!in_square_braces)
 				{
@@ -133,6 +146,7 @@ void OptimizedRegularExpressionImpl<b>::analyze(const std::string & regexp, std:
 				}
 				++pos;
 				break;
+
 			case '^': case '$': case '.': case '+':
 				is_trivial = false;
 				if (!last_substring->first.empty() && !in_square_braces)
@@ -142,6 +156,7 @@ void OptimizedRegularExpressionImpl<b>::analyze(const std::string & regexp, std:
 				}
 				++pos;
 				break;
+
 			/// Квантификаторы, допускающие нулевое количество.
 			case '{':
 				in_curly_braces = true;
@@ -155,10 +170,16 @@ void OptimizedRegularExpressionImpl<b>::analyze(const std::string & regexp, std:
 				}
 				++pos;
 				break;
+
 			case '}':
+				if (!in_curly_braces)
+					goto ordinary;
+
 				in_curly_braces = false;
 				++pos;
 				break;
+
+			ordinary:	/// Обычный, не заэскейпленный символ.
 			default:
 				if (depth == 0 && !in_curly_braces && !in_square_braces)
 				{

dbms/include/DB/Common/PODArray.h

@@ -29,14 +29,13 @@ namespace DB
   * Поддерживается только часть интерфейса std::vector.
   *
   * Конструктор по-умолчанию создаёт пустой объект, который не выделяет память.
-  * Затем выделяется память минимум под POD_ARRAY_INITIAL_SIZE элементов.
+  * Затем выделяется память минимум под INITIAL_SIZE элементов.
   *
   * Если вставлять элементы push_back-ом, не делая reserve, то PODArray примерно в 2.5 раза быстрее std::vector.
   */
-#define POD_ARRAY_INITIAL_SIZE 4096UL
 
-template <typename T>
-class PODArray : private boost::noncopyable, private Allocator	/// empty base optimization
+template <typename T, size_t INITIAL_SIZE = 4096, typename TAllocator = Allocator<false>>
+class PODArray : private boost::noncopyable, private TAllocator	/// empty base optimization
 {
 private:
 	char * c_start;
@@ -79,7 +78,7 @@ private:
 
 		size_t bytes_to_alloc = to_size(n);
 
-		c_start = c_end = reinterpret_cast<char *>(Allocator::alloc(bytes_to_alloc));
+		c_start = c_end = reinterpret_cast<char *>(TAllocator::alloc(bytes_to_alloc));
 		c_end_of_storage = c_start + bytes_to_alloc;
 	}
 
@@ -88,7 +87,7 @@ private:
 		if (c_start == nullptr)
 			return;
 
-		Allocator::free(c_start, storage_size());
+		TAllocator::free(c_start, storage_size());
 	}
 
 	void realloc(size_t n)
@@ -102,7 +101,7 @@ private:
 		ptrdiff_t end_diff = c_end - c_start;
 		size_t bytes_to_alloc = to_size(n);
 
-		c_start = reinterpret_cast<char *>(Allocator::realloc(c_start, storage_size(), bytes_to_alloc));
+		c_start = reinterpret_cast<char *>(TAllocator::realloc(c_start, storage_size(), bytes_to_alloc));
 
 		c_end = c_start + end_diff;
 		c_end_of_storage = c_start + bytes_to_alloc;
@@ -133,7 +132,17 @@ public:
     PODArray(const_iterator from_begin, const_iterator from_end) { alloc(from_end - from_begin); insert(from_begin, from_end); }
     ~PODArray() { dealloc(); }
 
-	PODArray(PODArray && other) { *this = std::move(other); }
+	PODArray(PODArray && other)
+	{
+		c_start = other.c_start;
+		c_end = other.c_end;
+		c_end_of_storage = other.c_end_of_storage;
+
+		other.c_start = nullptr;
+		other.c_end = nullptr;
+		other.c_end_of_storage = nullptr;
+	}
+
 	PODArray & operator=(PODArray && other)
 	{
 		std::swap(c_start, other.c_start);
@@ -174,7 +183,7 @@ public:
 	void reserve()
 	{
 		if (size() == 0)
-			realloc(POD_ARRAY_INITIAL_SIZE);
+			realloc(INITIAL_SIZE);
 		else
 			realloc(size() * 2);
 	}
@@ -227,6 +236,16 @@ public:
 		c_end += byte_size(1);
 	}
 
+	template <typename... Args>
+	void emplace_back(Args &&... args)
+	{
+		if (unlikely(c_end == c_end_of_storage))
+			reserve();
+
+		new (t_end()) T(std::forward<Args>(args)...);
+		c_end += byte_size(1);
+	}
+
 	/// Не вставляйте в массив кусок самого себя. Потому что при ресайзе, итераторы на самого себя могут инвалидироваться.
 	template <typename It1, typename It2>
 	void insert(It1 from_begin, It2 from_end)
@@ -246,7 +265,7 @@ public:
 		c_end += bytes_to_copy;
 	}
 
-	void swap(PODArray<T> & rhs)
+	void swap(PODArray & rhs)
 	{
 		std::swap(c_start, rhs.c_start);
 		std::swap(c_end, rhs.c_end);
@@ -271,13 +290,13 @@ public:
 		c_end = c_start + bytes_to_copy;
 	}
 
-	void assign(const PODArray<T> & from)
+	void assign(const PODArray & from)
 	{
 		assign(from.begin(), from.end());
 	}
 
 
-	bool operator== (const PODArray<T> & other) const
+	bool operator== (const PODArray & other) const
 	{
 		if (size() != other.size())
 			return false;
@@ -297,7 +316,7 @@ public:
 		return true;
 	}
 
-	bool operator!= (const PODArray<T> & other) const
+	bool operator!= (const PODArray & other) const
 	{
 		return !operator==(other);
 	}

dbms/include/DB/Common/SmallObjectPool.h

@@ -0,0 +1,88 @@
+#pragma once
+
+#include <DB/Core/ErrorCodes.h>
+#include <DB/Common/Arena.h>
+#include <common/likely.h>
+#include <ext/range.hpp>
+#include <ext/size.hpp>
+#include <ext/bit_cast.hpp>
+#include <cstdlib>
+#include <memory>
+
+
+namespace DB
+{
+
+
+class SmallObjectPool
+{
+private:
+	struct Block { Block * next; };
+
+	const std::size_t object_size;
+	Arena pool;
+	Block * free_list{};
+
+public:
+	SmallObjectPool(
+		const std::size_t object_size, const std::size_t initial_size = 4096, const std::size_t growth_factor = 2,
+		const std::size_t linear_growth_threshold = 128 * 1024 * 1024)
+		: object_size{object_size}, pool{initial_size, growth_factor, linear_growth_threshold}
+	{
+		if (object_size < sizeof(Block))
+			throw Exception{
+				"Can't make allocations smaller than sizeof(Block) = " + std::to_string(sizeof(Block)),
+				ErrorCodes::LOGICAL_ERROR
+			};
+
+		if (pool.size() < object_size)
+			return;
+
+		const auto num_objects = pool.size() / object_size;
+		auto head = free_list = ext::bit_cast<Block *>(pool.alloc(num_objects * object_size));
+
+		for (const auto i : ext::range(0, num_objects - 1))
+		{
+			(void) i;
+			head->next = ext::bit_cast<Block *>(ext::bit_cast<char *>(head) + object_size);
+			head = head->next;
+		}
+
+		head->next = nullptr;
+	}
+
+	char * alloc()
+	{
+		if (free_list)
+		{
+			const auto res = reinterpret_cast<char *>(free_list);
+			free_list = free_list->next;
+			return res;
+		}
+
+		return pool.alloc(object_size);
+	}
+
+	void free(const void * ptr)
+	{
+		union {
+			const void * p_v;
+			Block * block;
+		};
+
+		p_v = ptr;
+		block->next = free_list;
+
+		free_list = block;
+	}
+
+	/// Размер выделенного пула в байтах
+	size_t size() const
+	{
+		return pool.size();
+	}
+
+};
+
+
+}

dbms/include/DB/Core/Types.h

@@ -60,4 +60,7 @@ template <> struct TypeName<Float32> 	{ static std::string get() { return "Float
 template <> struct TypeName<Float64> 	{ static std::string get() { return "Float64"; 	} };
 template <> struct TypeName<String> 	{ static std::string get() { return "String"; 	} };
 
+/// Эти типы не поддерживаются СУБД. Но используются в других местах.
+template <> struct TypeName<long double>{ static std::string get() { return "long double"; } };
+
 }

dbms/include/DB/DataStreams/AddingDefaultBlockInputStream.h

@@ -30,11 +30,6 @@ public:
 		children.push_back(input_);
 	}
 
-	AddingDefaultBlockInputStream(BlockInputStreamPtr input_, NamesAndTypesListPtr required_columns_, const Context & context_)
-		: AddingDefaultBlockInputStream{input_, required_columns_, ColumnDefaults{}, context_}
-	{
-	}
-
 	String getName() const override { return "AddingDefault"; }
 
 	String getID() const override
@@ -65,7 +60,7 @@ protected:
 
 private:
 	NamesAndTypesListPtr required_columns;
-	const ColumnDefaults & column_defaults;
+	const ColumnDefaults column_defaults;
 	Context context;
 };
 

dbms/include/DB/DataStreams/AddingDefaultBlockOutputStream.h

@@ -58,7 +58,7 @@ public:
 private:
 	BlockOutputStreamPtr output;
 	NamesAndTypesListPtr required_columns;
-	const ColumnDefaults & column_defaults;
+	const ColumnDefaults column_defaults;
 	Context context;
 	bool only_explicit_column_defaults;
 };

dbms/include/DB/DataStreams/BinaryRowOutputStream.h

@@ -22,6 +22,8 @@ public:
 
 	void flush() override { ostr.next(); }
 
+	String getContentType() const override { return "application/octet-stream"; }
+
 protected:
 	WriteBuffer & ostr;
 	const Block sample;

dbms/include/DB/DataStreams/BlockOutputStreamFromRowOutputStream.h

@@ -24,6 +24,8 @@ public:
 	void setTotals(const Block & totals) override;
 	void setExtremes(const Block & extremes) override;
 
+	String getContentType() const override { return row_output->getContentType(); }
+
 private:
 	RowOutputStreamPtr row_output;
 	bool first_row;

dbms/include/DB/DataStreams/IBlockOutputStream.h

@@ -42,6 +42,10 @@ public:
 	virtual void setTotals(const Block & totals) {}
 	virtual void setExtremes(const Block & extremes) {}
 
+	/** Выставлять такой Content-Type при отдаче по HTTP.
+	  */
+	virtual String getContentType() const { return "text/plain; charset=UTF-8"; }
+
 	virtual ~IBlockOutputStream() {}
 
 	/** Не давать изменить таблицу, пока жив поток блоков.

dbms/include/DB/DataStreams/IProfilingBlockInputStream.h

@@ -169,6 +169,9 @@ protected:
 	/// Информация о приблизительном общем количестве строк собрана в родительском источнике.
 	bool collected_total_rows_approx = false;
 
+	/// Превышено ограничение на количество строк/байт, и нужно прекратить выполнение на следующем вызове read, как будто поток иссяк.
+	bool limit_exceeded_need_break = false;
+
 	/// Ограничения и квоты.
 
 	LocalLimits limits;

dbms/include/DB/DataStreams/IRowOutputStream.h

@@ -41,6 +41,9 @@ public:
 	virtual void setTotals(const Block & totals) {}
 	virtual void setExtremes(const Block & extremes) {}
 
+	/** Выставлять такой Content-Type при отдаче по HTTP. */
+	virtual String getContentType() const { return "text/plain; charset=UTF-8"; }
+
 	virtual ~IRowOutputStream() {}
 };
 

dbms/include/DB/DataStreams/JSONRowOutputStream.h

@@ -42,6 +42,8 @@ public:
 	void setTotals(const Block & totals_) override { totals = totals_; }
 	void setExtremes(const Block & extremes_) override { extremes = extremes_; }
 
+	String getContentType() const override { return "application/json; charset=UTF-8"; }
+
 protected:
 
 	void writeRowsBeforeLimitAtLeast();

dbms/include/DB/DataStreams/MaterializingBlockInputStream.h

@@ -38,9 +38,10 @@ protected:
 		size_t columns = res.columns();
 		for (size_t i = 0; i < columns; ++i)
 		{
-			ColumnPtr col = res.getByPosition(i).column;
-			if (col->isConst())
-				res.getByPosition(i).column = dynamic_cast<IColumnConst &>(*col).convertToFullColumn();
+			auto & src = res.getByPosition(i).column;
+			ColumnPtr converted = src->convertToFullColumnIfConst();
+			if (converted)
+				src = converted;
 		}
 
 		return res;

dbms/include/DB/DataStreams/MaterializingBlockOutputStream.h

@@ -23,9 +23,10 @@ public:
 
 		for (const auto i : ext::range(0, block.columns()))
 		{
-			ColumnPtr & col = block.getByPosition(i).column;
-			if (col->isConst())
-				col = dynamic_cast<IColumnConst &>(*col).convertToFullColumn();
+			auto & src = block.getByPosition(i).column;
+			ColumnPtr converted = src->convertToFullColumnIfConst();
+			if (converted)
+				src = converted;
 		}
 
 		output->write(block);

dbms/include/DB/DataStreams/NativeBlockOutputStream.h

@@ -30,6 +30,8 @@ public:
 
 	static void writeData(const IDataType & type, const ColumnPtr & column, WriteBuffer & ostr, size_t offset, size_t limit);
 
+	String getContentType() const override { return "application/octet-stream"; }
+
 private:
 	WriteBuffer & ostr;
 	UInt64 client_revision;

dbms/include/DB/DataStreams/ODBCBlockOutputStream.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <DB/DataStreams/IBlockOutputStream.h>
+
+
+namespace DB
+{
+
+/** Формат данных, предназначенный для упрощения реализации ODBC драйвера.
+  * ODBC драйвер предназначен для сборки под разные платформы без зависимостей от основного кода,
+  *  поэтому формат сделан так, чтобы в нём можно было как можно проще его распарсить.
+  * Выводится заголовок с нужной информацией.
+  * Затем данные выводятся в порядке строк. Каждое значение выводится так: длина в формате VarUInt, затем данные в текстовом виде.
+  */
+class ODBCBlockOutputStream : public IBlockOutputStream
+{
+public:
+	ODBCBlockOutputStream(WriteBuffer & out_);
+
+	void write(const Block & block) override;
+
+	void flush() override { out.next(); }
+	String getContentType() const override { return "application/octet-stream"; }
+
+private:
+	bool is_first = true;
+	WriteBuffer & out;
+};
+
+}

dbms/include/DB/DataStreams/RemoteBlockInputStream.h

@@ -3,67 +3,63 @@
 #include <common/logger_useful.h>
 
 #include <DB/DataStreams/IProfilingBlockInputStream.h>
-#include <DB/DataStreams/OneBlockInputStream.h>
-#include <DB/Common/VirtualColumnUtils.h>
 #include <DB/Common/Throttler.h>
 #include <DB/Interpreters/Context.h>
-
 #include <DB/Client/ConnectionPool.h>
-#include <DB/Client/ParallelReplicas.h>
-
+#include <DB/Client/MultiplexedConnections.h>
 
 namespace DB
 {
 
-/** Позволяет выполнить запрос (SELECT) на удалённых репликах одного шарда и получить результат.
+/** Позволяет выполнить запрос на удалённых репликах одного шарда и получить результат.
   */
 class RemoteBlockInputStream : public IProfilingBlockInputStream
 {
-private:
-	void init(const Settings * settings_)
-	{
-		if (settings_)
-		{
-			send_settings = true;
-			settings = *settings_;
-		}
-		else
-			send_settings = false;
-	}
-
 public:
 	/// Принимает готовое соединение.
-	RemoteBlockInputStream(Connection & connection_, const String & query_, const Settings * settings_, ThrottlerPtr throttler_ = nullptr,
-		const Tables & external_tables_ = Tables(), QueryProcessingStage::Enum stage_ = QueryProcessingStage::Complete,
-		const Context & context = getDefaultContext())
-		: connection(&connection_), query(query_), throttler(throttler_), external_tables(external_tables_), stage(stage_), context(context)
-	{
-		init(settings_);
-	}
+	RemoteBlockInputStream(Connection & connection_, const String & query_, const Settings * settings_,
+		ThrottlerPtr throttler_ = nullptr, const Tables & external_tables_ = Tables(),
+		QueryProcessingStage::Enum stage_ = QueryProcessingStage::Complete,
+		const Context & context_ = getDefaultContext());
 
 	/// Принимает готовое соединение. Захватывает владение соединением из пула.
-	RemoteBlockInputStream(ConnectionPool::Entry & pool_entry_, const String & query_, const Settings * settings_, ThrottlerPtr throttler_ = nullptr,
-		const Tables & external_tables_ = Tables(), QueryProcessingStage::Enum stage_ = QueryProcessingStage::Complete,
-		const Context & context = getDefaultContext())
-		: pool_entry(pool_entry_), connection(&*pool_entry_), query(query_), throttler(throttler_),
-		  external_tables(external_tables_), stage(stage_), context(context)
-	{
-		init(settings_);
-	}
+	RemoteBlockInputStream(ConnectionPool::Entry & pool_entry_, const String & query_, const Settings * settings_,
+		ThrottlerPtr throttler_ = nullptr, const Tables & external_tables_ = Tables(),
+		QueryProcessingStage::Enum stage_ = QueryProcessingStage::Complete,
+		const Context & context_ = getDefaultContext());
 
 	/// Принимает пул, из которого нужно будет достать одно или несколько соединений.
-	RemoteBlockInputStream(IConnectionPool * pool_, const String & query_, const Settings * settings_, ThrottlerPtr throttler_ = nullptr,
-		const Tables & external_tables_ = Tables(), QueryProcessingStage::Enum stage_ = QueryProcessingStage::Complete,
-		const Context & context = getDefaultContext())
-		: pool(pool_), query(query_), throttler(throttler_), external_tables(external_tables_), stage(stage_), context(context)
-	{
-		init(settings_);
-	}
+	RemoteBlockInputStream(IConnectionPool * pool_, const String & query_, const Settings * settings_,
+		ThrottlerPtr throttler_ = nullptr, const Tables & external_tables_ = Tables(),
+		QueryProcessingStage::Enum stage_ = QueryProcessingStage::Complete,
+		const Context & context_ = getDefaultContext());
 
+	/// Принимает пулы - один для каждого шарда, из которых нужно будет достать одно или несколько соединений.
+	RemoteBlockInputStream(ConnectionPoolsPtr & pools_, const String & query_, const Settings * settings_,
+		ThrottlerPtr throttler_ = nullptr, const Tables & external_tables_ = Tables(),
+		QueryProcessingStage::Enum stage_ = QueryProcessingStage::Complete,
+		const Context & context_ = getDefaultContext());
+
+	~RemoteBlockInputStream() override;
+
+	/// Отправить запрос на все существующие реплики.
+	void doBroadcast();
+
+	/// Кроме блоков, получить информацию о блоках.
+	void appendExtraInfo();
+
+	/// Отправляет запрос (инициирует вычисления) раньше, чем read.
+	void readPrefix() override;
+
+	/** Отменяем умолчальное уведомление о прогрессе,
+	  * так как колбэк прогресса вызывается самостоятельно.
+	  */
+	void progress(const Progress & value) override {}
+
+	void cancel() override;
 
 	String getName() const override { return "Remote"; }
 
-
 	String getID() const override
 	{
 		std::stringstream res;
@@ -71,249 +67,35 @@ public:
 		return res.str();
 	}
 
-
-	/** Отменяем умолчальное уведомление о прогрессе,
-	  * так как колбэк прогресса вызывается самостоятельно.
-	  */
-	void progress(const Progress & value) override {}
-
-
-	void cancel() override
-	{
-		bool old_val = false;
-		if (!is_cancelled.compare_exchange_strong(old_val, true, std::memory_order_seq_cst, std::memory_order_relaxed))
-			return;
-
-		{
-			std::lock_guard<std::mutex> lock(external_tables_mutex);
-
-			/// Останавливаем отправку внешних данных.
-			for (auto & vec : external_tables_data)
-				for (auto & elem : vec)
-					if (IProfilingBlockInputStream * stream = dynamic_cast<IProfilingBlockInputStream *>(elem.first.get()))
-						stream->cancel();
-		}
-
-		if (!isQueryPending() || hasThrownException())
-			return;
-
-		tryCancel("Cancelling query");
-	}
-
-
-	~RemoteBlockInputStream() override
-	{
-		/** Если прервались в середине цикла общения с репликами, то прервываем
-		  * все соединения, затем читаем и пропускаем оставшиеся пакеты чтобы
-		  * эти соединения не остались висеть в рассихронизированном состоянии.
-		  */
-		if (established || isQueryPending())
-			parallel_replicas->disconnect();
-	}
-
-
-	/// Отправляет запрос (инициирует вычисления) раньше, чем read.
-	void readPrefix() override
-	{
-		if (!sent_query)
-			sendQuery();
-	}
-
-	/// Отправить запрос на все существующие реплики.
-	void reachAllReplicas()
-	{
-		reach_all_replicas = true;
-	}
-
-	/// Кроме блоков, получить информацию о блоках.
-	void appendExtraInfo()
-	{
-		append_extra_info = true;
-	}
-
 	BlockExtraInfo getBlockExtraInfo() const override
 	{
-		return parallel_replicas->getBlockExtraInfo();
+		return multiplexed_connections->getBlockExtraInfo();
 	}
 
 protected:
 	/// Отправить на удаленные серверы все временные таблицы.
-	void sendExternalTables()
-	{
-		size_t count = parallel_replicas->size();
+	void sendExternalTables();
 
-		{
-			std::lock_guard<std::mutex> lock(external_tables_mutex);
+	Block readImpl() override;
 
-			external_tables_data.reserve(count);
-
-			for (size_t i = 0; i < count; ++i)
-			{
-				ExternalTablesData res;
-				for (const auto & table : external_tables)
-				{
-					StoragePtr cur = table.second;
-					QueryProcessingStage::Enum stage = QueryProcessingStage::Complete;
-					DB::BlockInputStreams input = cur->read(cur->getColumnNamesList(), ASTPtr(), context, settings,
-						stage, DEFAULT_BLOCK_SIZE, 1);
-					if (input.size() == 0)
-						res.push_back(std::make_pair(new OneBlockInputStream(cur->getSampleBlock()), table.first));
-					else
-						res.push_back(std::make_pair(input[0], table.first));
-				}
-				external_tables_data.push_back(std::move(res));
-			}
-		}
-
-		parallel_replicas->sendExternalTablesData(external_tables_data);
-	}
-
-
-	Block readImpl() override
-	{
-		if (!sent_query)
-		{
-			sendQuery();
-
-			if (settings.skip_unavailable_shards && 0 == parallel_replicas->size())
-				return {};
-		}
-
-		while (true)
-		{
-			if (isCancelled())
-				return Block();
-
-			Connection::Packet packet = parallel_replicas->receivePacket();
-
-			switch (packet.type)
-			{
-				case Protocol::Server::Data:
-					/// Если блок не пуст и не является заголовочным блоком
-					if (packet.block && packet.block.rows() > 0)
-						return packet.block;
-					break;	/// Если блок пустой - получим другие пакеты до EndOfStream.
-
-				case Protocol::Server::Exception:
-					got_exception_from_replica = true;
-					packet.exception->rethrow();
-					break;
-
-				case Protocol::Server::EndOfStream:
-					if (!parallel_replicas->hasActiveReplicas())
-					{
-						finished = true;
-						return Block();
-					}
-					break;
-
-				case Protocol::Server::Progress:
-					/** Используем прогресс с удалённого сервера.
-					  * В том числе, запишем его в ProcessList,
-					  *  и будем использовать его для проверки
-					  *  ограничений (например, минимальная скорость выполнения запроса)
-					  *  и квот (например, на количество строчек для чтения).
-					  */
-					progressImpl(packet.progress);
-					break;
-
-				case Protocol::Server::ProfileInfo:
-					info = packet.profile_info;
-					break;
-
-				case Protocol::Server::Totals:
-					totals = packet.block;
-					break;
-
-				case Protocol::Server::Extremes:
-					extremes = packet.block;
-					break;
-
-				default:
-					got_unknown_packet_from_replica = true;
-					throw Exception("Unknown packet from server", ErrorCodes::UNKNOWN_PACKET_FROM_SERVER);
-			}
-		}
-	}
-
-	void readSuffixImpl() override
-	{
-		/** Если одно из:
-		 *   - ничего не начинали делать;
-		 *   - получили все пакеты до EndOfStream;
-		 *   - получили с одной реплики эксепшен;
-		 *   - получили с одной реплики неизвестный пакет;
-		 * - то больше читать ничего не нужно.
-		 */
-		if (!isQueryPending() || hasThrownException())
-			return;
-
-		/** Если ещё прочитали не все данные, но они больше не нужны.
-		 * Это может быть из-за того, что данных достаточно (например, при использовании LIMIT).
-		 */
-
-		/// Отправим просьбу прервать выполнение запроса, если ещё не отправляли.
-		tryCancel("Cancelling query because enough data has been read");
-
-		/// Получим оставшиеся пакеты, чтобы не было рассинхронизации в соединениях с репликами.
-		Connection::Packet packet = parallel_replicas->drain();
-		switch (packet.type)
-		{
-			case Protocol::Server::EndOfStream:
-				finished = true;
-				break;
-
-			case Protocol::Server::Exception:
-				got_exception_from_replica = true;
-				packet.exception->rethrow();
-				break;
-
-			default:
-				got_unknown_packet_from_replica = true;
-				throw Exception("Unknown packet from server", ErrorCodes::UNKNOWN_PACKET_FROM_SERVER);
-		}
-	}
+	void readSuffixImpl() override;
 
 	/// Создать объект для общения с репликами одного шарда, на которых должен выполниться запрос.
-	void createParallelReplicas()
-	{
-		Settings * parallel_replicas_settings = send_settings ? &settings : nullptr;
-		if (connection != nullptr)
-			parallel_replicas = std::make_unique<ParallelReplicas>(connection, parallel_replicas_settings, throttler);
-		else
-			parallel_replicas = std::make_unique<ParallelReplicas>(pool, parallel_replicas_settings, throttler,
-				append_extra_info, reach_all_replicas);
-	}
+	void createMultiplexedConnections();
 
 	/// Возвращает true, если запрос отправлен.
-	bool isQueryPending() const
-	{
-		return sent_query && !finished;
-	}
+	bool isQueryPending() const;
 
 	/// Возвращает true, если исключение было выкинуто.
-	bool hasThrownException() const
-	{
-		return got_exception_from_replica || got_unknown_packet_from_replica;
-	}
+	bool hasThrownException() const;
 
 private:
-	void sendQuery()
-	{
-		createParallelReplicas();
+	void init(const Settings * settings_);
 
-		if (settings.skip_unavailable_shards && 0 == parallel_replicas->size())
-			return;
+	void sendQuery();
 
-		established = true;
-
-		parallel_replicas->sendQuery(query, "", stage, true);
-
-		established = false;
-		sent_query = true;
-
-		sendExternalTables();
-	}
+	/// Отправить запрос на отмену всех соединений к репликам, если такой запрос ещё не был отправлен.
+	void tryCancel(const char * reason);
 
 	/// ITable::read requires a Context, therefore we should create one if the user can't supply it
 	static Context & getDefaultContext()
@@ -322,23 +104,18 @@ private:
 		return instance;
 	}
 
-	/// Отправить запрос на отмену всех соединений к репликам, если такой запрос ещё не был отправлен.
-	void tryCancel(const char * reason)
-	{
-		bool old_val = false;
-		if (!was_cancelled.compare_exchange_strong(old_val, true, std::memory_order_seq_cst, std::memory_order_relaxed))
-			return;
-
-		LOG_TRACE(log, "(" << parallel_replicas->dumpAddresses() << ") " << reason);
-		parallel_replicas->sendCancel();
-	}
-
 private:
-	IConnectionPool * pool = nullptr;
-
+	/// Готовое соединение.
 	ConnectionPool::Entry pool_entry;
 	Connection * connection = nullptr;
-	std::unique_ptr<ParallelReplicas> parallel_replicas;
+
+	/// Пул соединений одного шарда.
+	IConnectionPool * pool = nullptr;
+
+	/// Пулы соединений одного или нескольких шардов.
+	ConnectionPoolsPtr pools;
+
+	std::unique_ptr<MultiplexedConnections> multiplexed_connections;
 
 	const String query;
 	bool send_settings;
@@ -384,7 +161,7 @@ private:
 	std::atomic<bool> got_unknown_packet_from_replica { false };
 
 	bool append_extra_info = false;
-	bool reach_all_replicas = false;
+	bool do_broadcast = false;
 
 	Logger * log = &Logger::get("RemoteBlockInputStream");
 };

dbms/include/DB/DataStreams/SummingSortedBlockInputStream.h

@@ -99,7 +99,7 @@ private:
 	/** Делаем поддержку двух разных курсоров - с Collation и без.
 	 *  Шаблоны используем вместо полиморфных SortCursor'ов и вызовов виртуальных функций.
 	 */
-	template<class TSortCursor>
+	template <class TSortCursor>
 	void merge(ColumnPlainPtrs & merged_columns, std::priority_queue<TSortCursor> & queue);
 
 	/// Вставить в результат просуммированную строку для текущей группы.
@@ -128,155 +128,14 @@ private:
 	/** Для вложенных Map выполняется слияние по ключу с выбрасыванием строк вложенных массивов, в которых
 	  * все элементы - нулевые.
 	  */
-	template<class TSortCursor>
-	bool mergeMaps(Row & row, TSortCursor & cursor)
-	{
-		auto non_empty_map_present = false;
-
-		/// merge nested maps
-		for (const auto & map : maps_to_sum)
-		{
-			const auto val_count = map.val_col_nums.size();
-
-			/// fetch key array reference from accumulator-row
-			auto & key_array_lhs = row[map.key_col_num].get<Array>();
-			/// returns a Field for pos-th item of val_index-th value
-			const auto val_getter_lhs = [&] (const auto val_index, const auto pos) -> decltype(auto) {
-				return row[map.val_col_nums[val_index]].get<Array>()[pos];
-			};
-
-			/// we will be sorting key positions, not the entire rows, to minimize actions
-			std::vector<std::size_t> key_pos_lhs(ext::range_iterator<std::size_t>{0},
-				ext::range_iterator<std::size_t>{key_array_lhs.size()});
-			std::sort(std::begin(key_pos_lhs), std::end(key_pos_lhs), [&] (const auto pos1, const auto pos2) {
-				return key_array_lhs[pos1] < key_array_lhs[pos2];
-			});
-
-			/// copy key field from current row under cursor
-			const auto key_field_rhs = (*cursor->all_columns[map.key_col_num])[cursor->pos];
-			/// for each element of `map.val_col_nums` copy corresponding array under cursor into vector
-			const auto val_fields_rhs = ext::map<std::vector>(map.val_col_nums,
-				[&] (const auto col_num) -> decltype(auto) {
-					return (*cursor->all_columns[col_num])[cursor->pos];
-				});
-
-			/// fetch key array reference from row under cursor
-			const auto & key_array_rhs = key_field_rhs.get<Array>();
-			/// returns a Field for pos-th item of val_index-th value
-			const auto val_getter_rhs = [&] (const auto val_index, const auto pos) -> decltype(auto) {
-				return val_fields_rhs[val_index].get<Array>()[pos];
-			};
-
-			std::vector<std::size_t> key_pos_rhs(ext::range_iterator<std::size_t>{0},
-				ext::range_iterator<std::size_t>{key_array_rhs.size()});
-			std::sort(std::begin(key_pos_rhs), std::end(key_pos_rhs), [&] (const auto pos1, const auto pos2) {
-				return key_array_rhs[pos1] < key_array_rhs[pos2];
-			});
-
-			/// max size after merge estimation
-			const auto max_size = key_pos_lhs.size() + key_pos_rhs.size();
-
-			/// create arrays with a single element (it will be overwritten on first iteration)
-			Array key_array_result(1);
-			key_array_result.reserve(max_size);
-			std::vector<Array> val_arrays_result(val_count, Array(1));
-			for (auto & val_array_result : val_arrays_result)
-				val_array_result.reserve(max_size);
-
-			/// discard first element
-			auto discard_prev = true;
-
-			/// either insert or merge new element
-			const auto insert_or_sum = [&] (std::size_t & index, const std::vector<std::size_t> & key_pos,
-											const auto & key_array, auto && val_getter) {
-				const auto pos = key_pos[index++];
-				const auto & key = key_array[pos];
-
-				if (discard_prev)
-				{
-					discard_prev = false;
-
-					key_array_result.back() = key;
-					for (const auto val_index : ext::range(0, val_count))
-						val_arrays_result[val_index].back() = val_getter(val_index, pos);
-				}
-				else if (key_array_result.back() == key)
-				{
-					/// merge with same key
-					auto should_discard = true;
-
-					for (const auto val_index : ext::range(0, val_count))
-						if (apply_visitor(FieldVisitorSum{val_getter(val_index, pos)},
-							val_arrays_result[val_index].back()))
-							should_discard = false;
-
-					discard_prev = should_discard;
-				}
-				else
-				{
-					/// append new key
-					key_array_result.emplace_back(key);
-					for (const auto val_index : ext::range(0, val_count))
-						val_arrays_result[val_index].emplace_back(val_getter(val_index, pos));
-				}
-			};
-
-			std::size_t index_lhs = 0;
-			std::size_t index_rhs = 0;
-
-			/// perform 2-way merge
-			while (true)
-				if (index_lhs < key_pos_lhs.size() && index_rhs == key_pos_rhs.size())
-					insert_or_sum(index_lhs, key_pos_lhs, key_array_lhs, val_getter_lhs);
-				else if (index_lhs == key_pos_lhs.size() && index_rhs < key_pos_rhs.size())
-					insert_or_sum(index_rhs, key_pos_rhs, key_array_rhs, val_getter_rhs);
-				else if (index_lhs < key_pos_lhs.size() && index_rhs < key_pos_rhs.size())
-					if (key_array_lhs[key_pos_lhs[index_lhs]] < key_array_rhs[key_pos_rhs[index_rhs]])
-						insert_or_sum(index_lhs, key_pos_lhs, key_array_lhs, val_getter_lhs);
-					else
-						insert_or_sum(index_rhs, key_pos_rhs, key_array_rhs, val_getter_rhs);
-				else
-					break;
-
-			/// discard last row if necessary
-			if (discard_prev)
-				key_array_result.pop_back();
-
-			/// store results into accumulator-row
-			key_array_lhs = std::move(key_array_result);
-			for (const auto val_col_index : ext::range(0, val_count))
-			{
-				/// discard last row if necessary
-				if (discard_prev)
-					val_arrays_result[val_col_index].pop_back();
-
-				row[map.val_col_nums[val_col_index]].get<Array>() = std::move(val_arrays_result[val_col_index]);
-			}
-
-			if (!key_array_lhs.empty())
-				non_empty_map_present = true;
-		}
-
-		return non_empty_map_present;
-	}
+	template <class TSortCursor>
+	bool mergeMaps(Row & row, TSortCursor & cursor);
 
 	/** Прибавить строчку под курсором к row.
 	  * Возвращает false, если результат получился нулевым.
 	  */
-	template<class TSortCursor>
-	bool addRow(Row & row, TSortCursor & cursor)
-	{
-		bool res = mergeMaps(row, cursor);	/// Есть ли хотя бы одно ненулевое число или непустой массив
-
-		for (size_t i = 0, size = column_numbers_to_sum.size(); i < size; ++i)
-		{
-			size_t j = column_numbers_to_sum[i];
-			if (apply_visitor(FieldVisitorSum((*cursor->all_columns[j])[cursor->pos]), row[j]))
-				res = true;
-		}
-
-		return res;
-	}
+	template <class TSortCursor>
+	bool addRow(Row & row, TSortCursor & cursor);
 };
 
 }

dbms/include/DB/DataStreams/TabSeparatedRowOutputStream.h

@@ -31,6 +31,9 @@ public:
 	void setTotals(const Block & totals_) override { totals = totals_; }
 	void setExtremes(const Block & extremes_) override { extremes = extremes_; }
 
+	/// https://www.iana.org/assignments/media-types/text/tab-separated-values
+	String getContentType() const override { return "text/tab-separated-values; charset=UTF-8"; }
+
 protected:
 	void writeTotals();
 	void writeExtremes();

dbms/include/DB/Dictionaries/CacheDictionary.h

@@ -5,8 +5,9 @@
 #include <DB/Dictionaries/DictionaryStructure.h>
 #include <DB/Common/HashTable/HashMap.h>
 #include <DB/Columns/ColumnString.h>
-#include <DB/Common/HashTable/HashMap.h>
 #include <ext/scope_guard.hpp>
+#include <ext/bit_cast.hpp>
+#include <ext/map.hpp>
 #include <Poco/RWLock.h>
 #include <cmath>
 #include <atomic>
@@ -127,31 +128,132 @@ public:
 		getItems(attribute, ids, out);
 	}
 
+#define DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(TYPE)\
+	void get##TYPE(\
+		const std::string & attribute_name, const PODArray<id_t> & ids, const PODArray<TYPE> & def,\
+		PODArray<TYPE> & out) const override\
+	{\
+		auto & attribute = getAttribute(attribute_name);\
+		if (attribute.type != AttributeUnderlyingType::TYPE)\
+			throw Exception{\
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),\
+				ErrorCodes::TYPE_MISMATCH\
+			};\
+		\
+		getItems<TYPE>(attribute, ids, out, &def);\
+	}
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt8)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt16)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt64)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int8)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int16)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int64)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Float32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Float64)
+#undef DECLARE_MULTIPLE_GETTER_WITH_DEFAULT
+	void getString(
+		const std::string & attribute_name, const PODArray<id_t> & ids, const ColumnString * const def,
+		ColumnString * const out) const override
+	{
+		auto & attribute = getAttribute(attribute_name);
+		if (attribute.type != AttributeUnderlyingType::String)
+			throw Exception{
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		getItems(attribute, ids, out, def);
+	}
+
+	void has(const PODArray<id_t> & ids, PODArray<UInt8> & out) const override
+	{
+		/// Mapping: <id> -> { all indices `i` of `ids` such that `ids[i]` = <id> }
+		MapType<std::vector<std::size_t>> outdated_ids;
+
+		const auto rows = ext::size(ids);
+		{
+			const Poco::ScopedReadRWLock read_lock{rw_lock};
+
+			const auto now = std::chrono::system_clock::now();
+			/// fetch up-to-date values, decide which ones require update
+			for (const auto i : ext::range(0, rows))
+			{
+				const auto id = ids[i];
+				const auto cell_idx = getCellIdx(id);
+				const auto & cell = cells[cell_idx];
+
+				/** cell should be updated if either:
+				 *	1. ids do not match,
+				 *	2. cell has expired,
+				 *	3. explicit defaults were specified and cell was set default. */
+				if (cell.id != id || cell.expiresAt() < now)
+					outdated_ids[id].push_back(i);
+				else
+					out[i] = !cell.isDefault();
+			}
+		}
+
+		query_count.fetch_add(rows, std::memory_order_relaxed);
+		hit_count.fetch_add(rows - outdated_ids.size(), std::memory_order_release);
+
+		if (outdated_ids.empty())
+			return;
+
+		std::vector<id_t> required_ids(outdated_ids.size());
+		std::transform(std::begin(outdated_ids), std::end(outdated_ids), std::begin(required_ids),
+			[] (auto & pair) { return pair.first; });
+
+		/// request new values
+		update(required_ids, [&] (const auto id, const auto) {
+			for (const auto out_idx : outdated_ids[id])
+				out[out_idx] = true;
+		}, [&] (const auto id, const auto) {
+			for (const auto out_idx : outdated_ids[id])
+				out[out_idx] = false;
+		});
+	}
+
 private:
+	template <typename Value> using MapType = HashMap<id_t, Value>;
+	template <typename Value> using ContainerType = Value[];
+	template <typename Value> using ContainerPtrType = std::unique_ptr<ContainerType<Value>>;
+
 	struct cell_metadata_t final
 	{
+		using time_point_t = std::chrono::system_clock::time_point;
+		using time_point_rep_t = time_point_t::rep;
+		using time_point_urep_t = std::make_unsigned_t<time_point_rep_t>;
+
+		static constexpr std::uint64_t EXPIRES_AT_MASK = std::numeric_limits<time_point_rep_t>::max();
+		static constexpr std::uint64_t IS_DEFAULT_MASK = ~EXPIRES_AT_MASK;
+
 		std::uint64_t id;
-		std::chrono::system_clock::time_point expires_at;
+		/// Stores both expiration time and `is_default` flag in the most significant bit
+		time_point_urep_t data;
+
+		/// Sets expiration time, resets `is_default` flag to false
+		time_point_t expiresAt() const { return ext::safe_bit_cast<time_point_t>(data & EXPIRES_AT_MASK); }
+		void setExpiresAt(const time_point_t & t) { data = ext::safe_bit_cast<time_point_urep_t>(t); }
+
+		bool isDefault() const { return (data & IS_DEFAULT_MASK) == IS_DEFAULT_MASK; }
+		void setDefault() { data |= IS_DEFAULT_MASK; }
 	};
 
 	struct attribute_t final
 	{
 		AttributeUnderlyingType type;
-		std::tuple<UInt8, UInt16, UInt32, UInt64,
+		std::tuple<
+			UInt8, UInt16, UInt32, UInt64,
 			Int8, Int16, Int32, Int64,
 			Float32, Float64,
 			String> null_values;
-		std::tuple<std::unique_ptr<UInt8[]>,
-			std::unique_ptr<UInt16[]>,
-			std::unique_ptr<UInt32[]>,
-			std::unique_ptr<UInt64[]>,
-			std::unique_ptr<Int8[]>,
-			std::unique_ptr<Int16[]>,
-			std::unique_ptr<Int32[]>,
-			std::unique_ptr<Int64[]>,
-			std::unique_ptr<Float32[]>,
-			std::unique_ptr<Float64[]>,
-			std::unique_ptr<StringRef[]>> arrays;
+		std::tuple<
+			ContainerPtrType<UInt8>, ContainerPtrType<UInt16>, ContainerPtrType<UInt32>, ContainerPtrType<UInt64>,
+			ContainerPtrType<Int8>, ContainerPtrType<Int16>, ContainerPtrType<Int32>, ContainerPtrType<Int64>,
+			ContainerPtrType<Float32>, ContainerPtrType<Float64>,
+			ContainerPtrType<StringRef>> arrays;
 	};
 
 	void createAttributes()
@@ -188,57 +290,57 @@ private:
 		{
 			case AttributeUnderlyingType::UInt8:
 				std::get<UInt8>(attr.null_values) = null_value.get<UInt64>();
-				std::get<std::unique_ptr<UInt8[]>>(attr.arrays) = std::make_unique<UInt8[]>(size);
+				std::get<ContainerPtrType<UInt8>>(attr.arrays) = std::make_unique<ContainerType<UInt8>>(size);
 				bytes_allocated += size * sizeof(UInt8);
 				break;
 			case AttributeUnderlyingType::UInt16:
 				std::get<UInt16>(attr.null_values) = null_value.get<UInt64>();
-				std::get<std::unique_ptr<UInt16[]>>(attr.arrays) = std::make_unique<UInt16[]>(size);
+				std::get<ContainerPtrType<UInt16>>(attr.arrays) = std::make_unique<ContainerType<UInt16>>(size);
 				bytes_allocated += size * sizeof(UInt16);
 				break;
 			case AttributeUnderlyingType::UInt32:
 				std::get<UInt32>(attr.null_values) = null_value.get<UInt64>();
-				std::get<std::unique_ptr<UInt32[]>>(attr.arrays) = std::make_unique<UInt32[]>(size);
+				std::get<ContainerPtrType<UInt32>>(attr.arrays) = std::make_unique<ContainerType<UInt32>>(size);
 				bytes_allocated += size * sizeof(UInt32);
 				break;
 			case AttributeUnderlyingType::UInt64:
 				std::get<UInt64>(attr.null_values) = null_value.get<UInt64>();
-				std::get<std::unique_ptr<UInt64[]>>(attr.arrays) = std::make_unique<UInt64[]>(size);
+				std::get<ContainerPtrType<UInt64>>(attr.arrays) = std::make_unique<ContainerType<UInt64>>(size);
 				bytes_allocated += size * sizeof(UInt64);
 				break;
 			case AttributeUnderlyingType::Int8:
 				std::get<Int8>(attr.null_values) = null_value.get<Int64>();
-				std::get<std::unique_ptr<Int8[]>>(attr.arrays) = std::make_unique<Int8[]>(size);
+				std::get<ContainerPtrType<Int8>>(attr.arrays) = std::make_unique<ContainerType<Int8>>(size);
 				bytes_allocated += size * sizeof(Int8);
 				break;
 			case AttributeUnderlyingType::Int16:
 				std::get<Int16>(attr.null_values) = null_value.get<Int64>();
-				std::get<std::unique_ptr<Int16[]>>(attr.arrays) = std::make_unique<Int16[]>(size);
+				std::get<ContainerPtrType<Int16>>(attr.arrays) = std::make_unique<ContainerType<Int16>>(size);
 				bytes_allocated += size * sizeof(Int16);
 				break;
 			case AttributeUnderlyingType::Int32:
 				std::get<Int32>(attr.null_values) = null_value.get<Int64>();
-				std::get<std::unique_ptr<Int32[]>>(attr.arrays) = std::make_unique<Int32[]>(size);
+				std::get<ContainerPtrType<Int32>>(attr.arrays) = std::make_unique<ContainerType<Int32>>(size);
 				bytes_allocated += size * sizeof(Int32);
 				break;
 			case AttributeUnderlyingType::Int64:
 				std::get<Int64>(attr.null_values) = null_value.get<Int64>();
-				std::get<std::unique_ptr<Int64[]>>(attr.arrays) = std::make_unique<Int64[]>(size);
+				std::get<ContainerPtrType<Int64>>(attr.arrays) = std::make_unique<ContainerType<Int64>>(size);
 				bytes_allocated += size * sizeof(Int64);
 				break;
 			case AttributeUnderlyingType::Float32:
 				std::get<Float32>(attr.null_values) = null_value.get<Float64>();
-				std::get<std::unique_ptr<Float32[]>>(attr.arrays) = std::make_unique<Float32[]>(size);
+				std::get<ContainerPtrType<Float32>>(attr.arrays) = std::make_unique<ContainerType<Float32>>(size);
 				bytes_allocated += size * sizeof(Float32);
 				break;
 			case AttributeUnderlyingType::Float64:
 				std::get<Float64>(attr.null_values) = null_value.get<Float64>();
-				std::get<std::unique_ptr<Float64[]>>(attr.arrays) = std::make_unique<Float64[]>(size);
+				std::get<ContainerPtrType<Float64>>(attr.arrays) = std::make_unique<ContainerType<Float64>>(size);
 				bytes_allocated += size * sizeof(Float64);
 				break;
 			case AttributeUnderlyingType::String:
 				std::get<String>(attr.null_values) = null_value.get<String>();
-				std::get<std::unique_ptr<StringRef[]>>(attr.arrays) = std::make_unique<StringRef[]>(size);
+				std::get<ContainerPtrType<StringRef>>(attr.arrays) = std::make_unique<ContainerType<StringRef>>(size);
 				bytes_allocated += size * sizeof(StringRef);
 				break;
 		}
@@ -247,64 +349,73 @@ private:
 	}
 
 	template <typename T>
-	void getItems(attribute_t & attribute, const PODArray<id_t> & ids, PODArray<T> & out) const
+	void getItems(
+		attribute_t & attribute, const PODArray<id_t> & ids, PODArray<T> & out,
+		const PODArray<T> * const def = nullptr) const
 	{
-		HashMap<id_t, std::vector<std::size_t>> outdated_ids;
-		auto & attribute_array = std::get<std::unique_ptr<T[]>>(attribute.arrays);
+		/// Mapping: <id> -> { all indices `i` of `ids` such that `ids[i]` = <id> }
+		MapType<std::vector<std::size_t>> outdated_ids;
+		auto & attribute_array = std::get<ContainerPtrType<T>>(attribute.arrays);
+		const auto rows = ext::size(ids);
 
 		{
 			const Poco::ScopedReadRWLock read_lock{rw_lock};
 
 			const auto now = std::chrono::system_clock::now();
 			/// fetch up-to-date values, decide which ones require update
-			for (const auto i : ext::range(0, ids.size()))
+			for (const auto i : ext::range(0, rows))
 			{
 				const auto id = ids[i];
-				if (id == 0)
-				{
-					out[i] = std::get<T>(attribute.null_values);
-					continue;
-				}
-
 				const auto cell_idx = getCellIdx(id);
 				const auto & cell = cells[cell_idx];
 
-				if (cell.id != id || cell.expires_at < now)
-				{
-					out[i] = std::get<T>(attribute.null_values);
+				/** cell should be updated if either:
+				 *	1. ids do not match,
+				 *	2. cell has expired,
+				 *	3. explicit defaults were specified and cell was set default. */
+				if (cell.id != id || cell.expiresAt() < now)
 					outdated_ids[id].push_back(i);
-				}
 				else
-					out[i] = attribute_array[cell_idx];
+					out[i] = def && cell.isDefault() ? (*def)[i] : attribute_array[cell_idx];
 			}
 		}
 
-		query_count.fetch_add(ids.size(), std::memory_order_relaxed);
-		hit_count.fetch_add(ids.size() - outdated_ids.size(), std::memory_order_release);
+		query_count.fetch_add(rows, std::memory_order_relaxed);
+		hit_count.fetch_add(rows - outdated_ids.size(), std::memory_order_release);
 
 		if (outdated_ids.empty())
 			return;
 
-		/// request new values
 		std::vector<id_t> required_ids(outdated_ids.size());
 		std::transform(std::begin(outdated_ids), std::end(outdated_ids), std::begin(required_ids),
 			[] (auto & pair) { return pair.first; });
 
+		/// request new values
 		update(required_ids, [&] (const auto id, const auto cell_idx) {
 			const auto attribute_value = attribute_array[cell_idx];
 
+			/// set missing values to out
+			for (const auto out_idx : outdated_ids[id])
+				out[out_idx] = attribute_value;
+		}, [&] (const auto id, const auto cell_idx) {
+			const auto attribute_value = !def ? attribute_array[cell_idx] : (*def)[outdated_ids[id].front()];
+
 			/// set missing values to out
 			for (const auto out_idx : outdated_ids[id])
 				out[out_idx] = attribute_value;
 		});
 	}
 
-	void getItems(attribute_t & attribute, const PODArray<id_t> & ids, ColumnString * out) const
+	void getItems(
+		attribute_t & attribute, const PODArray<id_t> & ids, ColumnString * out,
+		const ColumnString * const def = nullptr) const
 	{
-		/// save on some allocations
-		out->getOffsets().reserve(ids.size());
+		const auto rows = ext::size(ids);
 
-		auto & attribute_array = std::get<std::unique_ptr<StringRef[]>>(attribute.arrays);
+		/// save on some allocations
+		out->getOffsets().reserve(rows);
+
+		auto & attribute_array = std::get<ContainerPtrType<StringRef>>(attribute.arrays);
 
 		auto found_outdated_values = false;
 
@@ -314,20 +425,20 @@ private:
 
 			const auto now = std::chrono::system_clock::now();
 			/// fetch up-to-date values, discard on fail
-			for (const auto i : ext::range(0, ids.size()))
+			for (const auto i : ext::range(0, rows))
 			{
 				const auto id = ids[i];
 				const auto cell_idx = getCellIdx(id);
 				const auto & cell = cells[cell_idx];
 
-				if (cell.id != id || cell.expires_at < now)
+				if (cell.id != id || cell.expiresAt() < now)
 				{
 					found_outdated_values = true;
 					break;
 				}
 				else
 				{
-					const auto string_ref = attribute_array[cell_idx];
+					const auto string_ref = def && cell.isDefault() ? def->getDataAt(i) : attribute_array[cell_idx];
 					out->insertData(string_ref.data, string_ref.size);
 				}
 			}
@@ -336,19 +447,19 @@ private:
 		/// optimistic code completed successfully
 		if (!found_outdated_values)
 		{
-			query_count.fetch_add(ids.size(), std::memory_order_relaxed);
-			hit_count.fetch_add(ids.size(), std::memory_order_release);
+			query_count.fetch_add(rows, std::memory_order_relaxed);
+			hit_count.fetch_add(rows, std::memory_order_release);
 			return;
 		}
 
-		/// now onto the pessimistic one, discard possibly partial results from the optimistic path
+		/// now onto the pessimistic one, discard possible partial results from the optimistic path
 		out->getChars().resize_assume_reserved(0);
 		out->getOffsets().resize_assume_reserved(0);
 
-		/// outdated ids joined number of times they've been requested
-		HashMap<id_t, std::size_t> outdated_ids;
+		/// Mapping: <id> -> { all indices `i` of `ids` such that `ids[i]` = <id> }
+		MapType<std::vector<std::size_t>> outdated_ids;
 		/// we are going to store every string separately
-		HashMap<id_t, String> map;
+		MapType<String> map;
 
 		std::size_t total_length = 0;
 		{
@@ -361,19 +472,19 @@ private:
 				const auto cell_idx = getCellIdx(id);
 				const auto & cell = cells[cell_idx];
 
-				if (cell.id != id || cell.expires_at < now)
-					outdated_ids[id] += 1;
+				if (cell.id != id || cell.expiresAt() < now)
+					outdated_ids[id].push_back(i);
 				else
 				{
-					const auto string_ref = attribute_array[cell_idx];
+					const auto string_ref = def && cell.isDefault() ? def->getDataAt(i) : attribute_array[cell_idx];
 					map[id] = String{string_ref};
 					total_length += string_ref.size + 1;
 				}
 			}
 		}
 
-		query_count.fetch_add(ids.size(), std::memory_order_relaxed);
-		hit_count.fetch_add(ids.size() - outdated_ids.size(), std::memory_order_release);
+		query_count.fetch_add(rows, std::memory_order_relaxed);
+		hit_count.fetch_add(rows - outdated_ids.size(), std::memory_order_release);
 
 		/// request new values
 		if (!outdated_ids.empty())
@@ -386,28 +497,37 @@ private:
 				const auto attribute_value = attribute_array[cell_idx];
 
 				map[id] = String{attribute_value};
-				total_length += (attribute_value.size + 1) * outdated_ids[id];
+				total_length += (attribute_value.size + 1) * outdated_ids[id].size();
+			}, [&] (const auto id, const auto cell_idx) {
+				auto attribute_value = def ? def->getDataAt(outdated_ids[id].front()) : attribute_array[cell_idx];
+				map[id] = String{attribute_value};
+				total_length += (attribute_value.size + 1) * outdated_ids[id].size();
 			});
 		}
 
 		out->getChars().reserve(total_length);
 
+		const auto & null_value = std::get<String>(attribute.null_values);
+
 		for (const auto id : ids)
 		{
 			const auto it = map.find(id);
-			const auto string = it != map.end() ? it->second : std::get<String>(attribute.null_values);
+			/// @note check seems redundant, null_values are explicitly stored in the `map`
+			const auto & string = it != map.end() ? it->second : null_value;
 			out->insertData(string.data(), string.size());
 		}
 	}
 
-	template <typename F>
-	void update(const std::vector<id_t> ids, F && on_cell_updated) const
+	template <typename PresentIdHandler, typename AbsentIdHandler>
+	void update(
+		const std::vector<id_t> & requested_ids, PresentIdHandler && on_cell_updated,
+		AbsentIdHandler && on_id_not_found) const
 	{
-		auto stream = source_ptr->loadIds(ids);
+		auto stream = source_ptr->loadIds(requested_ids);
 		stream->readPrefix();
 
-		HashMap<UInt64, UInt8> remaining_ids{ids.size()};
-		for (const auto id : ids)
+		MapType<UInt8> remaining_ids{requested_ids.size()};
+		for (const auto id : requested_ids)
 			remaining_ids.insert({ id, 0 });
 
 		std::uniform_int_distribution<std::uint64_t> distribution{
@@ -429,9 +549,9 @@ private:
 			const auto & ids = id_column->getData();
 
 			/// cache column pointers
-			std::vector<const IColumn *> column_ptrs(attributes.size());
-			for (const auto i : ext::range(0, attributes.size()))
-				column_ptrs[i] = block.getByPosition(i + 1).column.get();
+			const auto column_ptrs = ext::map<std::vector>(ext::range(0, attributes.size()), [&block] (const auto & i) {
+				return block.getByPosition(i + 1).column.get();
+			});
 
 			for (const auto i : ext::range(0, ids.size()))
 			{
@@ -453,17 +573,20 @@ private:
 
 				cell.id = id;
 				if (dict_lifetime.min_sec != 0 && dict_lifetime.max_sec != 0)
-					cell.expires_at = std::chrono::system_clock::now() + std::chrono::seconds{distribution(rnd_engine)};
+					cell.setExpiresAt(std::chrono::system_clock::now() + std::chrono::seconds{distribution(rnd_engine)});
 				else
-					cell.expires_at = std::chrono::time_point<std::chrono::system_clock>::max();
+					cell.setExpiresAt(std::chrono::time_point<std::chrono::system_clock>::max());
 
+				/// inform caller
 				on_cell_updated(id, cell_idx);
+				/// mark corresponding id as found
 				remaining_ids[id] = 1;
 			}
 		}
 
 		stream->readSuffix();
 
+		/// Check which ids have not been found and require setting null_value
 		for (const auto id_found_pair : remaining_ids)
 		{
 			if (id_found_pair.second)
@@ -473,19 +596,24 @@ private:
 			const auto cell_idx = getCellIdx(id);
 			auto & cell = cells[cell_idx];
 
+			/// Set null_value for each attribute
 			for (auto & attribute : attributes)
 				setDefaultAttributeValue(attribute, cell_idx);
 
+			/// Check if cell had not been occupied before and increment element counter if it hadn't
 			if (cell.id == 0 && cell_idx != zero_cell_idx)
 				element_count.fetch_add(1, std::memory_order_relaxed);
 
 			cell.id = id;
 			if (dict_lifetime.min_sec != 0 && dict_lifetime.max_sec != 0)
-				cell.expires_at = std::chrono::system_clock::now() + std::chrono::seconds{distribution(rnd_engine)};
+				cell.setExpiresAt(std::chrono::system_clock::now() + std::chrono::seconds{distribution(rnd_engine)});
 			else
-				cell.expires_at = std::chrono::time_point<std::chrono::system_clock>::max();
+				cell.setExpiresAt(std::chrono::time_point<std::chrono::system_clock>::max());
 
-			on_cell_updated(id, cell_idx);
+			cell.setDefault();
+
+			/// inform caller that the cell has not been found
+			on_id_not_found(id, cell_idx);
 		}
 	}
 
@@ -500,20 +628,20 @@ private:
 	{
 		switch (attribute.type)
 		{
-			case AttributeUnderlyingType::UInt8: std::get<std::unique_ptr<UInt8[]>>(attribute.arrays)[idx] = std::get<UInt8>(attribute.null_values); break;
-			case AttributeUnderlyingType::UInt16: std::get<std::unique_ptr<UInt16[]>>(attribute.arrays)[idx] = std::get<UInt16>(attribute.null_values); break;
-			case AttributeUnderlyingType::UInt32: std::get<std::unique_ptr<UInt32[]>>(attribute.arrays)[idx] = std::get<UInt32>(attribute.null_values); break;
-			case AttributeUnderlyingType::UInt64: std::get<std::unique_ptr<UInt64[]>>(attribute.arrays)[idx] = std::get<UInt64>(attribute.null_values); break;
-			case AttributeUnderlyingType::Int8: std::get<std::unique_ptr<Int8[]>>(attribute.arrays)[idx] = std::get<Int8>(attribute.null_values); break;
-			case AttributeUnderlyingType::Int16: std::get<std::unique_ptr<Int16[]>>(attribute.arrays)[idx] = std::get<Int16>(attribute.null_values); break;
-			case AttributeUnderlyingType::Int32: std::get<std::unique_ptr<Int32[]>>(attribute.arrays)[idx] = std::get<Int32>(attribute.null_values); break;
-			case AttributeUnderlyingType::Int64: std::get<std::unique_ptr<Int64[]>>(attribute.arrays)[idx] = std::get<Int64>(attribute.null_values); break;
-			case AttributeUnderlyingType::Float32: std::get<std::unique_ptr<Float32[]>>(attribute.arrays)[idx] = std::get<Float32>(attribute.null_values); break;
-			case AttributeUnderlyingType::Float64: std::get<std::unique_ptr<Float64[]>>(attribute.arrays)[idx] = std::get<Float64>(attribute.null_values); break;
+			case AttributeUnderlyingType::UInt8: std::get<ContainerPtrType<UInt8>>(attribute.arrays)[idx] = std::get<UInt8>(attribute.null_values); break;
+			case AttributeUnderlyingType::UInt16: std::get<ContainerPtrType<UInt16>>(attribute.arrays)[idx] = std::get<UInt16>(attribute.null_values); break;
+			case AttributeUnderlyingType::UInt32: std::get<ContainerPtrType<UInt32>>(attribute.arrays)[idx] = std::get<UInt32>(attribute.null_values); break;
+			case AttributeUnderlyingType::UInt64: std::get<ContainerPtrType<UInt64>>(attribute.arrays)[idx] = std::get<UInt64>(attribute.null_values); break;
+			case AttributeUnderlyingType::Int8: std::get<ContainerPtrType<Int8>>(attribute.arrays)[idx] = std::get<Int8>(attribute.null_values); break;
+			case AttributeUnderlyingType::Int16: std::get<ContainerPtrType<Int16>>(attribute.arrays)[idx] = std::get<Int16>(attribute.null_values); break;
+			case AttributeUnderlyingType::Int32: std::get<ContainerPtrType<Int32>>(attribute.arrays)[idx] = std::get<Int32>(attribute.null_values); break;
+			case AttributeUnderlyingType::Int64: std::get<ContainerPtrType<Int64>>(attribute.arrays)[idx] = std::get<Int64>(attribute.null_values); break;
+			case AttributeUnderlyingType::Float32: std::get<ContainerPtrType<Float32>>(attribute.arrays)[idx] = std::get<Float32>(attribute.null_values); break;
+			case AttributeUnderlyingType::Float64: std::get<ContainerPtrType<Float64>>(attribute.arrays)[idx] = std::get<Float64>(attribute.null_values); break;
 			case AttributeUnderlyingType::String:
 			{
 				const auto & null_value_ref = std::get<String>(attribute.null_values);
-				auto & string_ref = std::get<std::unique_ptr<StringRef[]>>(attribute.arrays)[idx];
+				auto & string_ref = std::get<ContainerPtrType<StringRef>>(attribute.arrays)[idx];
 				if (string_ref.data == null_value_ref.data())
 					return;
 
@@ -532,20 +660,20 @@ private:
 	{
 		switch (attribute.type)
 		{
-			case AttributeUnderlyingType::UInt8: std::get<std::unique_ptr<UInt8[]>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
-			case AttributeUnderlyingType::UInt16: std::get<std::unique_ptr<UInt16[]>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
-			case AttributeUnderlyingType::UInt32: std::get<std::unique_ptr<UInt32[]>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
-			case AttributeUnderlyingType::UInt64: std::get<std::unique_ptr<UInt64[]>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
-			case AttributeUnderlyingType::Int8: std::get<std::unique_ptr<Int8[]>>(attribute.arrays)[idx] = value.get<Int64>(); break;
-			case AttributeUnderlyingType::Int16: std::get<std::unique_ptr<Int16[]>>(attribute.arrays)[idx] = value.get<Int64>(); break;
-			case AttributeUnderlyingType::Int32: std::get<std::unique_ptr<Int32[]>>(attribute.arrays)[idx] = value.get<Int64>(); break;
-			case AttributeUnderlyingType::Int64: std::get<std::unique_ptr<Int64[]>>(attribute.arrays)[idx] = value.get<Int64>(); break;
-			case AttributeUnderlyingType::Float32: std::get<std::unique_ptr<Float32[]>>(attribute.arrays)[idx] = value.get<Float64>(); break;
-			case AttributeUnderlyingType::Float64: std::get<std::unique_ptr<Float64[]>>(attribute.arrays)[idx] = value.get<Float64>(); break;
+			case AttributeUnderlyingType::UInt8: std::get<ContainerPtrType<UInt8>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
+			case AttributeUnderlyingType::UInt16: std::get<ContainerPtrType<UInt16>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
+			case AttributeUnderlyingType::UInt32: std::get<ContainerPtrType<UInt32>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
+			case AttributeUnderlyingType::UInt64: std::get<ContainerPtrType<UInt64>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
+			case AttributeUnderlyingType::Int8: std::get<ContainerPtrType<Int8>>(attribute.arrays)[idx] = value.get<Int64>(); break;
+			case AttributeUnderlyingType::Int16: std::get<ContainerPtrType<Int16>>(attribute.arrays)[idx] = value.get<Int64>(); break;
+			case AttributeUnderlyingType::Int32: std::get<ContainerPtrType<Int32>>(attribute.arrays)[idx] = value.get<Int64>(); break;
+			case AttributeUnderlyingType::Int64: std::get<ContainerPtrType<Int64>>(attribute.arrays)[idx] = value.get<Int64>(); break;
+			case AttributeUnderlyingType::Float32: std::get<ContainerPtrType<Float32>>(attribute.arrays)[idx] = value.get<Float64>(); break;
+			case AttributeUnderlyingType::Float64: std::get<ContainerPtrType<Float64>>(attribute.arrays)[idx] = value.get<Float64>(); break;
 			case AttributeUnderlyingType::String:
 			{
 				const auto & string = value.get<String>();
-				auto & string_ref = std::get<std::unique_ptr<StringRef[]>>(attribute.arrays)[idx];
+				auto & string_ref = std::get<ContainerPtrType<StringRef>>(attribute.arrays)[idx];
 				const auto & null_value_ref = std::get<String>(attribute.null_values);
 				if (string_ref.data != null_value_ref.data())
 				{

dbms/include/DB/Dictionaries/ClickHouseDictionarySource.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <DB/Dictionaries/IDictionarySource.h>
+#include <DB/Dictionaries/DictionaryStructure.h>
 #include <DB/Client/ConnectionPool.h>
 #include <DB/DataStreams/RemoteBlockInputStream.h>
 #include <DB/Interpreters/executeQuery.h>
@@ -40,7 +41,8 @@ public:
 			  max_connections, host, port, db, user, password,
 			  "ClickHouseDictionarySource")
 		  },
-		  load_all_query{composeLoadAllQuery()}
+		  load_all_query{composeLoadAllQuery()},
+		  key_tuple_definition{dict_struct.key ? composeKeyTupleDefinition() : std::string{}}
 	{}
 
 	/// copy-constructor is provided in order to support cloneability
@@ -69,11 +71,13 @@ public:
 
 	BlockInputStreamPtr loadIds(const std::vector<std::uint64_t> & ids) override
 	{
-		const auto query = composeLoadIdsQuery(ids);
+		return createStreamForSelectiveLoad(composeLoadIdsQuery(ids));
+	}
 
-		if (is_local)
-			return executeQuery(query, context, true).in;
-		return new RemoteBlockInputStream{pool.get(), query, nullptr};
+	BlockInputStreamPtr loadKeys(
+		const ConstColumnPlainPtrs & key_columns, const std::vector<std::size_t> & requested_rows) override
+	{
+		return createStreamForSelectiveLoad(composeLoadKeysQuery(key_columns, requested_rows));
 	}
 
 	bool isModified() const override { return true; }
@@ -95,13 +99,15 @@ private:
 			WriteBufferFromString out{query};
 			writeString("SELECT ", out);
 
-			if (!dict_struct.id.expression.empty())
+			if (dict_struct.id)
 			{
-				writeParenthesisedString(dict_struct.id.expression, out);
+				if (!dict_struct.id->expression.empty())
+				{
+					writeParenthesisedString(dict_struct.id->expression, out);
 					writeString(" AS ", out);
 				}
 
-			writeProbablyBackQuotedString(dict_struct.id.name, out);
+				writeProbablyBackQuotedString(dict_struct.id->name, out);
 
 				if (dict_struct.range_min && dict_struct.range_max)
 				{
@@ -125,6 +131,26 @@ private:
 
 					writeProbablyBackQuotedString(dict_struct.range_max->name, out);
 				}
+			}
+			else if (dict_struct.key)
+			{
+				auto first = true;
+				for (const auto & key : *dict_struct.key)
+				{
+					if (!first)
+						writeString(", ", out);
+
+					first = false;
+
+					if (!key.expression.empty())
+					{
+						writeParenthesisedString(key.expression, out);
+						writeString(" AS ", out);
+					}
+
+					writeProbablyBackQuotedString(key.name, out);
+				}
+			}
 
 			for (const auto & attr : dict_struct.attributes)
 			{
@@ -161,19 +187,22 @@ private:
 
 	std::string composeLoadIdsQuery(const std::vector<std::uint64_t> ids)
 	{
+		if (!dict_struct.id)
+			throw Exception{"Simple key required for method", ErrorCodes::UNSUPPORTED_METHOD};
+
 		std::string query;
 
 		{
 			WriteBufferFromString out{query};
 			writeString("SELECT ", out);
 
-			if (!dict_struct.id.expression.empty())
+			if (!dict_struct.id->expression.empty())
 			{
-				writeParenthesisedString(dict_struct.id.expression, out);
+				writeParenthesisedString(dict_struct.id->expression, out);
 				writeString(" AS ", out);
 			}
 
-			writeProbablyBackQuotedString(dict_struct.id.name, out);
+			writeProbablyBackQuotedString(dict_struct.id->name, out);
 
 			for (const auto & attr : dict_struct.attributes)
 			{
@@ -204,7 +233,7 @@ private:
 				writeString(" AND ", out);
 			}
 
-			writeProbablyBackQuotedString(dict_struct.id.name, out);
+			writeProbablyBackQuotedString(dict_struct.id->name, out);
 			writeString(" IN (", out);
 
 			auto first = true;
@@ -223,6 +252,118 @@ private:
 		return query;
 	}
 
+	std::string composeLoadKeysQuery(
+		const ConstColumnPlainPtrs & key_columns, const std::vector<std::size_t> & requested_rows)
+	{
+		if (!dict_struct.key)
+			throw Exception{"Composite key required for method", ErrorCodes::UNSUPPORTED_METHOD};
+
+		std::string query;
+
+		{
+			WriteBufferFromString out{query};
+			writeString("SELECT ", out);
+
+			auto first = true;
+			for (const auto & key_or_attribute : boost::join(*dict_struct.key, dict_struct.attributes))
+			{
+				if (!first)
+					writeString(", ", out);
+
+				first = false;
+
+				if (!key_or_attribute.expression.empty())
+				{
+					writeParenthesisedString(key_or_attribute.expression, out);
+					writeString(" AS ", out);
+				}
+
+				writeProbablyBackQuotedString(key_or_attribute.name, out);
+			}
+
+			writeString(" FROM ", out);
+			if (!db.empty())
+			{
+				writeProbablyBackQuotedString(db, out);
+				writeChar('.', out);
+			}
+			writeProbablyBackQuotedString(table, out);
+
+			writeString(" WHERE ", out);
+
+			if (!where.empty())
+			{
+				writeString(where, out);
+				writeString(" AND ", out);
+			}
+
+			writeString(key_tuple_definition, out);
+			writeString(" IN (", out);
+
+			first = true;
+			for (const auto row : requested_rows)
+			{
+				if (!first)
+					writeString(", ", out);
+
+				first = false;
+				composeKeyTuple(key_columns, row, out);
+			}
+
+			writeString(");", out);
+		}
+
+		return query;
+	}
+
+	std::string composeKeyTupleDefinition() const
+	{
+		if (!dict_struct.key)
+			throw Exception{"Composite key required for method", ErrorCodes::UNSUPPORTED_METHOD};
+
+		std::string result{"("};
+
+		auto first = true;
+		for (const auto & key : *dict_struct.key)
+		{
+			if (!first)
+				result += ", ";
+
+			first = false;
+			result += key.name;
+		}
+
+		result += ")";
+
+		return result;
+	}
+
+	void composeKeyTuple(const ConstColumnPlainPtrs & key_columns, const std::size_t row, WriteBuffer & out) const
+	{
+		writeString("(", out);
+
+		const auto keys_size = key_columns.size();
+		auto first = true;
+		for (const auto i : ext::range(0, keys_size))
+		{
+			if (!first)
+				writeString(", ", out);
+
+			first = false;
+			const auto & value = (*key_columns[i])[row];
+			(*dict_struct.key)[i].type->serializeTextQuoted(value, out);
+		}
+
+		writeString(")", out);
+	}
+
+	BlockInputStreamPtr createStreamForSelectiveLoad(const std::string query)
+	{
+		if (is_local)
+			return executeQuery(query, context, true).in;
+		return new RemoteBlockInputStream{pool.get(), query, nullptr};
+	}
+
 	const DictionaryStructure dict_struct;
 	const std::string host;
 	const UInt16 port;
@@ -236,6 +377,7 @@ private:
 	const bool is_local;
 	std::unique_ptr<ConnectionPool> pool;
 	const std::string load_all_query;
+	const std::string key_tuple_definition;
 };
 
 }

dbms/include/DB/Dictionaries/ComplexKeyCacheDictionary.h

@@ -0,0 +1,941 @@
+#pragma once
+
+#include <DB/Dictionaries/IDictionary.h>
+#include <DB/Dictionaries/IDictionarySource.h>
+#include <DB/Dictionaries/DictionaryStructure.h>
+#include <DB/Common/Arena.h>
+#include <DB/Common/ArenaWithFreeLists.h>
+#include <DB/Common/SmallObjectPool.h>
+#include <DB/Common/HashTable/HashMap.h>
+#include <DB/Columns/ColumnString.h>
+#include <DB/Core/StringRef.h>
+#include <ext/scope_guard.hpp>
+#include <ext/bit_cast.hpp>
+#include <ext/range.hpp>
+#include <ext/map.hpp>
+#include <Poco/RWLock.h>
+#include <cmath>
+#include <atomic>
+#include <chrono>
+#include <vector>
+#include <map>
+#include <tuple>
+#include <DB/DataStreams/NullBlockInputStream.h>
+
+
+namespace DB
+{
+
+class ComplexKeyCacheDictionary final : public IDictionaryBase
+{
+public:
+	ComplexKeyCacheDictionary(const std::string & name, const DictionaryStructure & dict_struct,
+		DictionarySourcePtr source_ptr, const DictionaryLifetime dict_lifetime,
+		const std::size_t size)
+		: name{name}, dict_struct(dict_struct), source_ptr{std::move(source_ptr)}, dict_lifetime(dict_lifetime),
+		  size{round_up_to_power_of_two(size)}
+	{
+		if (!this->source_ptr->supportsSelectiveLoad())
+			throw Exception{
+				name + ": source cannot be used with ComplexKeyCacheDictionary",
+				ErrorCodes::UNSUPPORTED_METHOD
+			};
+
+		createAttributes();
+	}
+
+	ComplexKeyCacheDictionary(const ComplexKeyCacheDictionary & other)
+		: ComplexKeyCacheDictionary{other.name, other.dict_struct, other.source_ptr->clone(), other.dict_lifetime, other.size}
+	{}
+
+	std::string getKeyDescription() const { return key_description; };
+
+	std::exception_ptr getCreationException() const override { return {}; }
+
+	std::string getName() const override { return name; }
+
+	std::string getTypeName() const override { return "ComplexKeyCache"; }
+
+	std::size_t getBytesAllocated() const override
+	{
+		return bytes_allocated + key_size_is_fixed ? fixed_size_keys_pool->size() : keys_pool->size();
+	}
+
+	std::size_t getQueryCount() const override { return query_count.load(std::memory_order_relaxed); }
+
+	double getHitRate() const override
+	{
+		return static_cast<double>(hit_count.load(std::memory_order_acquire)) /
+			query_count.load(std::memory_order_relaxed);
+	}
+
+	std::size_t getElementCount() const override { return element_count.load(std::memory_order_relaxed); }
+
+	double getLoadFactor() const override
+	{
+		return static_cast<double>(element_count.load(std::memory_order_relaxed)) / size;
+	}
+
+	bool isCached() const override { return true; }
+
+	DictionaryPtr clone() const override { return std::make_unique<ComplexKeyCacheDictionary>(*this); }
+
+	const IDictionarySource * getSource() const override { return source_ptr.get(); }
+
+	const DictionaryLifetime & getLifetime() const override { return dict_lifetime; }
+
+	const DictionaryStructure & getStructure() const override { return dict_struct; }
+
+	std::chrono::time_point<std::chrono::system_clock> getCreationTime() const override
+	{
+		return creation_time;
+	}
+
+	bool isInjective(const std::string & attribute_name) const override
+	{
+		return dict_struct.attributes[&getAttribute(attribute_name) - attributes.data()].injective;
+	}
+
+#define DECLARE_MULTIPLE_GETTER(TYPE)\
+	void get##TYPE(\
+		const std::string & attribute_name, const ConstColumnPlainPtrs & key_columns, const DataTypes & key_types,\
+		PODArray<TYPE> & out) const\
+	{\
+		validateKeyTypes(key_types);\
+		\
+		auto & attribute = getAttribute(attribute_name);\
+		if (attribute.type != AttributeUnderlyingType::TYPE)\
+			throw Exception{\
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),\
+				ErrorCodes::TYPE_MISMATCH\
+			};\
+		\
+		getItems<TYPE>(attribute, key_columns, out);\
+	}
+	DECLARE_MULTIPLE_GETTER(UInt8)
+	DECLARE_MULTIPLE_GETTER(UInt16)
+	DECLARE_MULTIPLE_GETTER(UInt32)
+	DECLARE_MULTIPLE_GETTER(UInt64)
+	DECLARE_MULTIPLE_GETTER(Int8)
+	DECLARE_MULTIPLE_GETTER(Int16)
+	DECLARE_MULTIPLE_GETTER(Int32)
+	DECLARE_MULTIPLE_GETTER(Int64)
+	DECLARE_MULTIPLE_GETTER(Float32)
+	DECLARE_MULTIPLE_GETTER(Float64)
+#undef DECLARE_MULTIPLE_GETTER
+	void getString(
+		const std::string & attribute_name, const ConstColumnPlainPtrs & key_columns, const DataTypes & key_types,
+		ColumnString * out) const
+	{
+		validateKeyTypes(key_types);
+
+		auto & attribute = getAttribute(attribute_name);
+		if (attribute.type != AttributeUnderlyingType::String)
+			throw Exception{
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		getItems(attribute, key_columns, out);
+	}
+
+#define DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(TYPE)\
+	void get##TYPE(\
+		const std::string & attribute_name, const ConstColumnPlainPtrs & key_columns, const DataTypes & key_types,\
+		const PODArray<TYPE> & def, PODArray<TYPE> & out) const\
+	{\
+		validateKeyTypes(key_types);\
+		\
+		auto & attribute = getAttribute(attribute_name);\
+		if (attribute.type != AttributeUnderlyingType::TYPE)\
+			throw Exception{\
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),\
+				ErrorCodes::TYPE_MISMATCH\
+			};\
+		\
+		getItems<TYPE>(attribute, key_columns, out, &def);\
+	}
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt8)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt16)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt64)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int8)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int16)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int64)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Float32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Float64)
+#undef DECLARE_MULTIPLE_GETTER_WITH_DEFAULT
+	void getString(
+		const std::string & attribute_name, const ConstColumnPlainPtrs & key_columns, const DataTypes & key_types,
+		const ColumnString * const def, ColumnString * const out) const
+	{
+		validateKeyTypes(key_types);
+
+		auto & attribute = getAttribute(attribute_name);
+		if (attribute.type != AttributeUnderlyingType::String)
+			throw Exception{
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		getItems(attribute, key_columns, out, def);
+	}
+
+	void has(const ConstColumnPlainPtrs & key_columns, const DataTypes & key_types, PODArray<UInt8> & out) const
+	{
+		validateKeyTypes(key_types);
+
+		/// Mapping: <key> -> { all indices `i` of `key_columns` such that `key_columns[i]` = <key> }
+		MapType<std::vector<std::size_t>> outdated_keys;
+
+		const auto rows = key_columns.front()->size();
+		const auto keys_size = dict_struct.key->size();
+		StringRefs keys(keys_size);
+		Arena temporary_keys_pool;
+		PODArray<StringRef> keys_array(rows);
+
+		{
+			const Poco::ScopedReadRWLock read_lock{rw_lock};
+
+			const auto now = std::chrono::system_clock::now();
+			/// fetch up-to-date values, decide which ones require update
+			for (const auto row : ext::range(0, rows))
+			{
+				const auto key = placeKeysInPool(row, key_columns, keys, temporary_keys_pool);
+				keys_array[row] = key;
+				const auto hash = StringRefHash{}(key);
+				const auto cell_idx = hash & (size - 1);
+				const auto & cell = cells[cell_idx];
+
+				/** cell should be updated if either:
+				 *	1. keys (or hash) do not match,
+				 *	2. cell has expired,
+				 *	3. explicit defaults were specified and cell was set default. */
+				if (cell.hash != hash || cell.key != key || cell.expiresAt() < now)
+					outdated_keys[key].push_back(row);
+				else
+					out[row] = !cell.isDefault();
+			}
+		}
+
+		query_count.fetch_add(rows, std::memory_order_relaxed);
+		hit_count.fetch_add(rows - outdated_keys.size(), std::memory_order_release);
+
+		if (outdated_keys.empty())
+			return;
+
+		std::vector<std::size_t> required_rows(outdated_keys.size());
+		std::transform(std::begin(outdated_keys), std::end(outdated_keys), std::begin(required_rows),
+			[] (auto & pair) { return pair.second.front(); });
+
+		/// request new values
+		update(key_columns, keys_array, required_rows, [&] (const auto key, const auto) {
+			for (const auto out_idx : outdated_keys[key])
+				out[out_idx] = true;
+		}, [&] (const auto key, const auto) {
+			for (const auto out_idx : outdated_keys[key])
+				out[out_idx] = false;
+		});
+	}
+
+private:
+	template <typename Value> using MapType = HashMapWithSavedHash<StringRef, Value, StringRefHash>;
+	template <typename Value> using ContainerType = Value[];
+	template <typename Value> using ContainerPtrType = std::unique_ptr<ContainerType<Value>>;
+
+	struct cell_metadata_t final
+	{
+		using time_point_t = std::chrono::system_clock::time_point;
+		using time_point_rep_t = time_point_t::rep;
+		using time_point_urep_t = std::make_unsigned_t<time_point_rep_t>;
+
+		static constexpr std::uint64_t EXPIRES_AT_MASK = std::numeric_limits<time_point_rep_t>::max();
+		static constexpr std::uint64_t IS_DEFAULT_MASK = ~EXPIRES_AT_MASK;
+
+		StringRef key;
+		decltype(StringRefHash{}(key)) hash;
+		/// Stores both expiration time and `is_default` flag in the most significant bit
+		time_point_urep_t data;
+
+		/// Sets expiration time, resets `is_default` flag to false
+		time_point_t expiresAt() const { return ext::safe_bit_cast<time_point_t>(data & EXPIRES_AT_MASK); }
+		void setExpiresAt(const time_point_t & t) { data = ext::safe_bit_cast<time_point_urep_t>(t); }
+
+		bool isDefault() const { return (data & IS_DEFAULT_MASK) == IS_DEFAULT_MASK; }
+		void setDefault() { data |= IS_DEFAULT_MASK; }
+	};
+
+	struct attribute_t final
+	{
+		AttributeUnderlyingType type;
+		std::tuple<
+			UInt8, UInt16, UInt32, UInt64,
+			Int8, Int16, Int32, Int64,
+			Float32, Float64,
+			String> null_values;
+		std::tuple<
+			ContainerPtrType<UInt8>, ContainerPtrType<UInt16>, ContainerPtrType<UInt32>, ContainerPtrType<UInt64>,
+			ContainerPtrType<Int8>, ContainerPtrType<Int16>, ContainerPtrType<Int32>, ContainerPtrType<Int64>,
+			ContainerPtrType<Float32>, ContainerPtrType<Float64>,
+			ContainerPtrType<StringRef>> arrays;
+	};
+
+	void createAttributes()
+	{
+		const auto size = dict_struct.attributes.size();
+		attributes.reserve(size);
+
+		bytes_allocated += size * sizeof(cell_metadata_t);
+		bytes_allocated += size * sizeof(attributes.front());
+
+		for (const auto & attribute : dict_struct.attributes)
+		{
+			attribute_index_by_name.emplace(attribute.name, attributes.size());
+			attributes.push_back(createAttributeWithType(attribute.underlying_type, attribute.null_value));
+
+			if (attribute.hierarchical)
+				throw Exception{
+					name + ": hierarchical attributes not supported for dictionary of type " + getTypeName(),
+					ErrorCodes::TYPE_MISMATCH
+				};
+		}
+	}
+
+	attribute_t createAttributeWithType(const AttributeUnderlyingType type, const Field & null_value)
+	{
+		attribute_t attr{type};
+
+		switch (type)
+		{
+			case AttributeUnderlyingType::UInt8:
+				std::get<UInt8>(attr.null_values) = null_value.get<UInt64>();
+				std::get<ContainerPtrType<UInt8>>(attr.arrays) = std::make_unique<ContainerType<UInt8>>(size);
+				bytes_allocated += size * sizeof(UInt8);
+				break;
+			case AttributeUnderlyingType::UInt16:
+				std::get<UInt16>(attr.null_values) = null_value.get<UInt64>();
+				std::get<ContainerPtrType<UInt16>>(attr.arrays) = std::make_unique<ContainerType<UInt16>>(size);
+				bytes_allocated += size * sizeof(UInt16);
+				break;
+			case AttributeUnderlyingType::UInt32:
+				std::get<UInt32>(attr.null_values) = null_value.get<UInt64>();
+				std::get<ContainerPtrType<UInt32>>(attr.arrays) = std::make_unique<ContainerType<UInt32>>(size);
+				bytes_allocated += size * sizeof(UInt32);
+				break;
+			case AttributeUnderlyingType::UInt64:
+				std::get<UInt64>(attr.null_values) = null_value.get<UInt64>();
+				std::get<ContainerPtrType<UInt64>>(attr.arrays) = std::make_unique<ContainerType<UInt64>>(size);
+				bytes_allocated += size * sizeof(UInt64);
+				break;
+			case AttributeUnderlyingType::Int8:
+				std::get<Int8>(attr.null_values) = null_value.get<Int64>();
+				std::get<ContainerPtrType<Int8>>(attr.arrays) = std::make_unique<ContainerType<Int8>>(size);
+				bytes_allocated += size * sizeof(Int8);
+				break;
+			case AttributeUnderlyingType::Int16:
+				std::get<Int16>(attr.null_values) = null_value.get<Int64>();
+				std::get<ContainerPtrType<Int16>>(attr.arrays) = std::make_unique<ContainerType<Int16>>(size);
+				bytes_allocated += size * sizeof(Int16);
+				break;
+			case AttributeUnderlyingType::Int32:
+				std::get<Int32>(attr.null_values) = null_value.get<Int64>();
+				std::get<ContainerPtrType<Int32>>(attr.arrays) = std::make_unique<ContainerType<Int32>>(size);
+				bytes_allocated += size * sizeof(Int32);
+				break;
+			case AttributeUnderlyingType::Int64:
+				std::get<Int64>(attr.null_values) = null_value.get<Int64>();
+				std::get<ContainerPtrType<Int64>>(attr.arrays) = std::make_unique<ContainerType<Int64>>(size);
+				bytes_allocated += size * sizeof(Int64);
+				break;
+			case AttributeUnderlyingType::Float32:
+				std::get<Float32>(attr.null_values) = null_value.get<Float64>();
+				std::get<ContainerPtrType<Float32>>(attr.arrays) = std::make_unique<ContainerType<Float32>>(size);
+				bytes_allocated += size * sizeof(Float32);
+				break;
+			case AttributeUnderlyingType::Float64:
+				std::get<Float64>(attr.null_values) = null_value.get<Float64>();
+				std::get<ContainerPtrType<Float64>>(attr.arrays) = std::make_unique<ContainerType<Float64>>(size);
+				bytes_allocated += size * sizeof(Float64);
+				break;
+			case AttributeUnderlyingType::String:
+				std::get<String>(attr.null_values) = null_value.get<String>();
+				std::get<ContainerPtrType<StringRef>>(attr.arrays) = std::make_unique<ContainerType<StringRef>>(size);
+				bytes_allocated += size * sizeof(StringRef);
+				break;
+		}
+
+		return attr;
+	}
+
+	static std::string createKeyDescription(const DictionaryStructure & dict_struct)
+	{
+		std::ostringstream out;
+
+		out << '(';
+
+		auto first = true;
+		for (const auto & key : *dict_struct.key)
+		{
+			if (!first)
+				out << ", ";
+
+			first = false;
+
+			out << key.type->getName();
+		}
+
+		out << ')';
+
+		return out.str();
+	}
+
+	void validateKeyTypes(const DataTypes & key_types) const
+	{
+		if (key_types.size() != dict_struct.key->size())
+			throw Exception{
+				"Key structure does not match, expected " + key_description,
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		for (const auto i : ext::range(0, key_types.size()))
+		{
+			const auto & expected_type = (*dict_struct.key)[i].type->getName();
+			const auto & actual_type = key_types[i]->getName();
+
+			if (expected_type != actual_type)
+				throw Exception{
+					"Key type at position " + std::to_string(i) + " does not match, expected " + expected_type +
+						", found " + actual_type,
+					ErrorCodes::TYPE_MISMATCH
+				};
+		}
+	}
+
+	template <typename T>
+	void getItems(
+		attribute_t & attribute, const ConstColumnPlainPtrs & key_columns, PODArray<T> & out,
+		const PODArray<T> * const def = nullptr) const
+	{
+		/// Mapping: <key> -> { all indices `i` of `key_columns` such that `key_columns[i]` = <key> }
+		MapType<std::vector<std::size_t>> outdated_keys;
+		auto & attribute_array = std::get<ContainerPtrType<T>>(attribute.arrays);
+
+		const auto rows = key_columns.front()->size();
+		const auto keys_size = dict_struct.key->size();
+		StringRefs keys(keys_size);
+		Arena temporary_keys_pool;
+		PODArray<StringRef> keys_array(rows);
+
+		{
+			const Poco::ScopedReadRWLock read_lock{rw_lock};
+
+			const auto now = std::chrono::system_clock::now();
+			/// fetch up-to-date values, decide which ones require update
+			for (const auto row : ext::range(0, rows))
+			{
+				const auto key = placeKeysInPool(row, key_columns, keys, temporary_keys_pool);
+				keys_array[row] = key;
+				const auto hash = StringRefHash{}(key);
+				const auto cell_idx = hash & (size - 1);
+				const auto & cell = cells[cell_idx];
+
+				/** cell should be updated if either:
+				 *	1. keys (or hash) do not match,
+				 *	2. cell has expired,
+				 *	3. explicit defaults were specified and cell was set default. */
+				if (cell.hash != hash || cell.key != key || cell.expiresAt() < now)
+					outdated_keys[key].push_back(row);
+				else
+					out[row] =  def && cell.isDefault() ? (*def)[row] : attribute_array[cell_idx];
+			}
+		}
+
+		query_count.fetch_add(rows, std::memory_order_relaxed);
+		hit_count.fetch_add(rows - outdated_keys.size(), std::memory_order_release);
+
+		if (outdated_keys.empty())
+			return;
+
+		std::vector<std::size_t> required_rows(outdated_keys.size());
+		std::transform(std::begin(outdated_keys), std::end(outdated_keys), std::begin(required_rows),
+			[] (auto & pair) { return pair.second.front(); });
+
+		/// request new values
+		update(key_columns, keys_array, required_rows, [&] (const auto key, const auto cell_idx) {
+			const auto attribute_value = attribute_array[cell_idx];
+
+			for (const auto out_idx : outdated_keys[key])
+				out[out_idx] = attribute_value;
+		}, [&] (const auto key, const auto cell_idx) {
+			const auto attribute_value = !def ? attribute_array[cell_idx] : (*def)[outdated_keys[key].front()];
+
+			for (const auto out_idx : outdated_keys[key])
+				out[out_idx] = attribute_value;
+		});
+	}
+
+	void getItems(
+		attribute_t & attribute, const ConstColumnPlainPtrs & key_columns, ColumnString * out,
+		const ColumnString * const def = nullptr) const
+	{
+		const auto rows = key_columns.front()->size();
+		/// save on some allocations
+		out->getOffsets().reserve(rows);
+
+		const auto keys_size = dict_struct.key->size();
+		StringRefs keys(keys_size);
+		Arena temporary_keys_pool;
+
+		auto & attribute_array = std::get<ContainerPtrType<StringRef>>(attribute.arrays);
+
+		auto found_outdated_values = false;
+
+		/// perform optimistic version, fallback to pessimistic if failed
+		{
+			const Poco::ScopedReadRWLock read_lock{rw_lock};
+
+			const auto now = std::chrono::system_clock::now();
+			/// fetch up-to-date values, discard on fail
+			for (const auto row : ext::range(0, rows))
+			{
+				const auto key = placeKeysInPool(row, key_columns, keys, temporary_keys_pool);
+				SCOPE_EXIT(temporary_keys_pool.rollback(key.size));
+				const auto hash = StringRefHash{}(key);
+				const auto cell_idx = hash & (size - 1);
+				const auto & cell = cells[cell_idx];
+
+				if (cell.hash != hash || cell.key != key || cell.expiresAt() < now)
+				{
+					found_outdated_values = true;
+					break;
+				}
+				else
+				{
+					const auto string_ref =  def && cell.isDefault() ? def->getDataAt(row) : attribute_array[cell_idx];
+					out->insertData(string_ref.data, string_ref.size);
+				}
+			}
+		}
+
+		/// optimistic code completed successfully
+		if (!found_outdated_values)
+		{
+			query_count.fetch_add(rows, std::memory_order_relaxed);
+			hit_count.fetch_add(rows, std::memory_order_release);
+			return;
+		}
+
+		/// now onto the pessimistic one, discard possible partial results from the optimistic path
+		out->getChars().resize_assume_reserved(0);
+		out->getOffsets().resize_assume_reserved(0);
+
+		/// Mapping: <key> -> { all indices `i` of `key_columns` such that `key_columns[i]` = <key> }
+		MapType<std::vector<std::size_t>> outdated_keys;
+		/// we are going to store every string separately
+		MapType<String> map;
+		PODArray<StringRef> keys_array(rows);
+
+		std::size_t total_length = 0;
+		{
+			const Poco::ScopedReadRWLock read_lock{rw_lock};
+
+			const auto now = std::chrono::system_clock::now();
+			for (const auto row : ext::range(0, rows))
+			{
+				const auto key = placeKeysInPool(row, key_columns, keys, temporary_keys_pool);
+				keys_array[row] = key;
+				const auto hash = StringRefHash{}(key);
+				const auto cell_idx = hash & (size - 1);
+				const auto & cell = cells[cell_idx];
+
+				if (cell.hash != hash || cell.key != key || cell.expiresAt() < now)
+					outdated_keys[key].push_back(row);
+				else
+				{
+					const auto string_ref =  def && cell.isDefault() ? def->getDataAt(row) : attribute_array[cell_idx];
+					map[key] = String{string_ref};
+					total_length += string_ref.size + 1;
+				}
+			}
+		}
+
+		query_count.fetch_add(rows, std::memory_order_relaxed);
+		hit_count.fetch_add(rows - outdated_keys.size(), std::memory_order_release);
+
+		/// request new values
+		if (!outdated_keys.empty())
+		{
+			std::vector<std::size_t> required_rows(outdated_keys.size());
+			std::transform(std::begin(outdated_keys), std::end(outdated_keys), std::begin(required_rows),
+				[] (auto & pair) { return pair.second.front(); });
+
+			update(key_columns, keys_array, required_rows, [&] (const auto key, const auto cell_idx) {
+				const auto attribute_value = attribute_array[cell_idx];
+
+				map[key] = String{attribute_value};
+				total_length += (attribute_value.size + 1) * outdated_keys[key].size();
+			}, [&] (const auto key, const auto cell_idx) {
+				auto attribute_value = def ? def->getDataAt(outdated_keys[key].front()) : attribute_array[cell_idx];
+				map[key] = String{attribute_value};
+				total_length += (attribute_value.size + 1) * outdated_keys[key].size();
+			});
+		}
+
+		out->getChars().reserve(total_length);
+
+		const auto & null_value = std::get<String>(attribute.null_values);
+
+		for (const auto key : keys_array)
+		{
+			const auto it = map.find(key);
+			/// @note check seems redundant, null_values are explicitly stored in the `map`
+			const auto & string = it != map.end() ? it->second : null_value;
+			out->insertData(string.data(), string.size());
+		}
+	}
+
+	template <typename PresentKeyHandler, typename AbsentKeyHandler>
+	void update(
+		const ConstColumnPlainPtrs & in_key_columns, const PODArray<StringRef> & in_keys,
+		const std::vector<std::size_t> & in_requested_rows, PresentKeyHandler && on_cell_updated,
+		AbsentKeyHandler && on_key_not_found) const
+	{
+		auto stream = source_ptr->loadKeys(in_key_columns, in_requested_rows);
+		stream->readPrefix();
+
+		MapType<UInt8> remaining_keys{in_requested_rows.size()};
+		for (const auto row : in_requested_rows)
+			remaining_keys.insert({ in_keys[row], 0 });
+
+		std::uniform_int_distribution<std::uint64_t> distribution{
+			dict_lifetime.min_sec,
+			dict_lifetime.max_sec
+		};
+
+		const Poco::ScopedWriteRWLock write_lock{rw_lock};
+
+		const auto keys_size = dict_struct.key->size();
+		StringRefs keys(keys_size);
+
+		const auto attributes_size = attributes.size();
+
+		while (const auto block = stream->read())
+		{
+			/// cache column pointers
+			const auto key_columns = ext::map<ConstColumnPlainPtrs>(ext::range(0, keys_size),
+				[&] (const std::size_t attribute_idx) {
+					return block.getByPosition(attribute_idx).column.get();
+				});
+
+			const auto attribute_columns = ext::map<ConstColumnPlainPtrs>(ext::range(0, attributes_size),
+				[&] (const std::size_t attribute_idx) {
+					return block.getByPosition(keys_size + attribute_idx).column.get();
+				});
+
+			const auto rows = block.rowsInFirstColumn();
+
+			for (const auto row : ext::range(0, rows))
+			{
+				auto key = allocKey(row, key_columns, keys);
+				const auto hash = StringRefHash{}(key);
+				const auto cell_idx = hash & (size - 1);
+				auto & cell = cells[cell_idx];
+
+				for (const auto attribute_idx : ext::range(0, attributes.size()))
+				{
+					const auto & attribute_column = *attribute_columns[attribute_idx];
+					auto & attribute = attributes[attribute_idx];
+
+					setAttributeValue(attribute, cell_idx, attribute_column[row]);
+				}
+
+				/// if cell id is zero and zero does not map to this cell, then the cell is unused
+				if (cell.key == StringRef{} && cell_idx != zero_cell_idx)
+					element_count.fetch_add(1, std::memory_order_relaxed);
+
+				/// handle memory allocated for old key
+				if (key == cell.key)
+				{
+					freeKey(key);
+					key = cell.key;
+				}
+				else
+				{
+					/// new key is different from the old one
+					if (cell.key.data)
+						freeKey(cell.key);
+
+					cell.key = key;
+				}
+
+				cell.hash = hash;
+
+				if (dict_lifetime.min_sec != 0 && dict_lifetime.max_sec != 0)
+					cell.setExpiresAt(std::chrono::system_clock::now() + std::chrono::seconds{distribution(rnd_engine)});
+				else
+					cell.setExpiresAt(std::chrono::time_point<std::chrono::system_clock>::max());
+
+				/// inform caller
+				on_cell_updated(key, cell_idx);
+				/// mark corresponding id as found
+				remaining_keys[key] = 1;
+			}
+		}
+
+		stream->readSuffix();
+
+		/// Check which ids have not been found and require setting null_value
+		for (const auto key_found_pair : remaining_keys)
+		{
+			if (key_found_pair.second)
+				continue;
+
+			auto key = key_found_pair.first;
+			const auto hash = StringRefHash{}(key);
+			const auto cell_idx = hash & (size - 1);
+			auto & cell = cells[cell_idx];
+
+			/// Set null_value for each attribute
+			for (auto & attribute : attributes)
+				setDefaultAttributeValue(attribute, cell_idx);
+
+			/// Check if cell had not been occupied before and increment element counter if it hadn't
+			if (cell.key == StringRef{} && cell_idx != zero_cell_idx)
+				element_count.fetch_add(1, std::memory_order_relaxed);
+
+			if (key == cell.key)
+				key = cell.key;
+			else
+			{
+				if (cell.key.data)
+					freeKey(cell.key);
+
+				/// copy key from temporary pool
+				key = copyKey(key);
+				cell.key = key;
+			}
+
+			cell.hash = hash;
+
+			if (dict_lifetime.min_sec != 0 && dict_lifetime.max_sec != 0)
+				cell.setExpiresAt(std::chrono::system_clock::now() + std::chrono::seconds{distribution(rnd_engine)});
+			else
+				cell.setExpiresAt(std::chrono::time_point<std::chrono::system_clock>::max());
+
+			cell.setDefault();
+
+			/// inform caller that the cell has not been found
+			on_key_not_found(key, cell_idx);
+		}
+	}
+
+	std::uint64_t getCellIdx(const StringRef key) const
+	{
+		const auto hash = StringRefHash{}(key);
+		const auto idx = hash & (size - 1);
+		return idx;
+	}
+
+	void setDefaultAttributeValue(attribute_t & attribute, const std::size_t idx) const
+	{
+		switch (attribute.type)
+		{
+			case AttributeUnderlyingType::UInt8: std::get<ContainerPtrType<UInt8>>(attribute.arrays)[idx] = std::get<UInt8>(attribute.null_values); break;
+			case AttributeUnderlyingType::UInt16: std::get<ContainerPtrType<UInt16>>(attribute.arrays)[idx] = std::get<UInt16>(attribute.null_values); break;
+			case AttributeUnderlyingType::UInt32: std::get<ContainerPtrType<UInt32>>(attribute.arrays)[idx] = std::get<UInt32>(attribute.null_values); break;
+			case AttributeUnderlyingType::UInt64: std::get<ContainerPtrType<UInt64>>(attribute.arrays)[idx] = std::get<UInt64>(attribute.null_values); break;
+			case AttributeUnderlyingType::Int8: std::get<ContainerPtrType<Int8>>(attribute.arrays)[idx] = std::get<Int8>(attribute.null_values); break;
+			case AttributeUnderlyingType::Int16: std::get<ContainerPtrType<Int16>>(attribute.arrays)[idx] = std::get<Int16>(attribute.null_values); break;
+			case AttributeUnderlyingType::Int32: std::get<ContainerPtrType<Int32>>(attribute.arrays)[idx] = std::get<Int32>(attribute.null_values); break;
+			case AttributeUnderlyingType::Int64: std::get<ContainerPtrType<Int64>>(attribute.arrays)[idx] = std::get<Int64>(attribute.null_values); break;
+			case AttributeUnderlyingType::Float32: std::get<ContainerPtrType<Float32>>(attribute.arrays)[idx] = std::get<Float32>(attribute.null_values); break;
+			case AttributeUnderlyingType::Float64: std::get<ContainerPtrType<Float64>>(attribute.arrays)[idx] = std::get<Float64>(attribute.null_values); break;
+			case AttributeUnderlyingType::String:
+			{
+				const auto & null_value_ref = std::get<String>(attribute.null_values);
+				auto & string_ref = std::get<ContainerPtrType<StringRef>>(attribute.arrays)[idx];
+				if (string_ref.data == null_value_ref.data())
+					return;
+
+				if (string_ref.size != 0)
+					bytes_allocated -= string_ref.size + 1;
+				const std::unique_ptr<const char[]> deleter{string_ref.data};
+
+				string_ref = StringRef{null_value_ref};
+
+				break;
+			}
+		}
+	}
+
+	void setAttributeValue(attribute_t & attribute, const std::size_t idx, const Field & value) const
+	{
+		switch (attribute.type)
+		{
+			case AttributeUnderlyingType::UInt8: std::get<ContainerPtrType<UInt8>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
+			case AttributeUnderlyingType::UInt16: std::get<ContainerPtrType<UInt16>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
+			case AttributeUnderlyingType::UInt32: std::get<ContainerPtrType<UInt32>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
+			case AttributeUnderlyingType::UInt64: std::get<ContainerPtrType<UInt64>>(attribute.arrays)[idx] = value.get<UInt64>(); break;
+			case AttributeUnderlyingType::Int8: std::get<ContainerPtrType<Int8>>(attribute.arrays)[idx] = value.get<Int64>(); break;
+			case AttributeUnderlyingType::Int16: std::get<ContainerPtrType<Int16>>(attribute.arrays)[idx] = value.get<Int64>(); break;
+			case AttributeUnderlyingType::Int32: std::get<ContainerPtrType<Int32>>(attribute.arrays)[idx] = value.get<Int64>(); break;
+			case AttributeUnderlyingType::Int64: std::get<ContainerPtrType<Int64>>(attribute.arrays)[idx] = value.get<Int64>(); break;
+			case AttributeUnderlyingType::Float32: std::get<ContainerPtrType<Float32>>(attribute.arrays)[idx] = value.get<Float64>(); break;
+			case AttributeUnderlyingType::Float64: std::get<ContainerPtrType<Float64>>(attribute.arrays)[idx] = value.get<Float64>(); break;
+			case AttributeUnderlyingType::String:
+			{
+				const auto & string = value.get<String>();
+				auto & string_ref = std::get<ContainerPtrType<StringRef>>(attribute.arrays)[idx];
+				const auto & null_value_ref = std::get<String>(attribute.null_values);
+				if (string_ref.data != null_value_ref.data())
+				{
+					if (string_ref.size != 0)
+						bytes_allocated -= string_ref.size + 1;
+					/// avoid explicit delete, let unique_ptr handle it
+					const std::unique_ptr<const char[]> deleter{string_ref.data};
+				}
+
+				const auto size = string.size();
+				if (size != 0)
+				{
+					auto string_ptr = std::make_unique<char[]>(size + 1);
+					std::copy(string.data(), string.data() + size + 1, string_ptr.get());
+					string_ref = StringRef{string_ptr.release(), size};
+					bytes_allocated += size + 1;
+				}
+				else
+					string_ref = {};
+
+				break;
+			}
+		}
+	}
+
+	attribute_t & getAttribute(const std::string & attribute_name) const
+	{
+		const auto it = attribute_index_by_name.find(attribute_name);
+		if (it == std::end(attribute_index_by_name))
+			throw Exception{
+				name + ": no such attribute '" + attribute_name + "'",
+				ErrorCodes::BAD_ARGUMENTS
+			};
+
+		return attributes[it->second];
+	}
+
+	StringRef allocKey(const std::size_t row, const ConstColumnPlainPtrs & key_columns, StringRefs & keys) const
+	{
+		if (key_size_is_fixed)
+			return placeKeysInFixedSizePool(row, key_columns);
+
+		return placeKeysInPool(row, key_columns, keys, *keys_pool);
+	}
+
+	void freeKey(const StringRef key) const
+	{
+		if (key_size_is_fixed)
+			fixed_size_keys_pool->free(key.data);
+		else
+			keys_pool->free(key.data, key.size);
+	}
+
+	static std::size_t round_up_to_power_of_two(std::size_t n)
+	{
+		--n;
+		n |= n >> 1;
+		n |= n >> 2;
+		n |= n >> 4;
+		n |= n >> 8;
+		n |= n >> 16;
+		n |= n >> 32;
+		++n;
+
+		return n;
+	}
+
+	static std::uint64_t getSeed()
+	{
+		timespec ts;
+		clock_gettime(CLOCK_MONOTONIC, &ts);
+		return ts.tv_nsec ^ getpid();
+	}
+
+	template <typename Arena>
+	static StringRef placeKeysInPool(
+		const std::size_t row, const ConstColumnPlainPtrs & key_columns, StringRefs & keys, Arena & pool)
+	{
+		const auto keys_size = key_columns.size();
+		size_t sum_keys_size{};
+		for (const auto i : ext::range(0, keys_size))
+		{
+			keys[i] = key_columns[i]->getDataAtWithTerminatingZero(row);
+			sum_keys_size += keys[i].size;
+		}
+
+		const auto res = pool.alloc(sum_keys_size);
+		auto place = res;
+
+		for (size_t j = 0; j < keys_size; ++j)
+		{
+			memcpy(place, keys[j].data, keys[j].size);
+			place += keys[j].size;
+		}
+
+		return { res, sum_keys_size };
+	}
+
+	StringRef placeKeysInFixedSizePool(
+		const std::size_t row, const ConstColumnPlainPtrs & key_columns) const
+	{
+		const auto res = fixed_size_keys_pool->alloc();
+		auto place = res;
+
+		for (const auto & key_column : key_columns)
+		{
+			const auto key = key_column->getDataAt(row);
+			memcpy(place, key.data, key.size);
+			place += key.size;
+		}
+
+		return { res, key_size };
+	}
+
+	StringRef copyKey(const StringRef key) const
+	{
+		const auto res = key_size_is_fixed ? fixed_size_keys_pool->alloc() : keys_pool->alloc(key.size);
+		memcpy(res, key.data, key.size);
+
+		return { res, key.size };
+	}
+
+	const std::string name;
+	const DictionaryStructure dict_struct;
+	const DictionarySourcePtr source_ptr;
+	const DictionaryLifetime dict_lifetime;
+	const std::string key_description{createKeyDescription(dict_struct)};
+
+	mutable Poco::RWLock rw_lock;
+	const std::size_t size;
+	const std::uint64_t zero_cell_idx{getCellIdx(StringRef{})};
+	std::map<std::string, std::size_t> attribute_index_by_name;
+	mutable std::vector<attribute_t> attributes;
+	mutable std::vector<cell_metadata_t> cells{size};
+	const bool key_size_is_fixed{dict_struct.isKeySizeFixed()};
+	std::size_t key_size{key_size_is_fixed ? dict_struct.getKeySize() : 0};
+	std::unique_ptr<ArenaWithFreeLists> keys_pool = key_size_is_fixed ? nullptr :
+		std::make_unique<ArenaWithFreeLists>();
+	std::unique_ptr<SmallObjectPool> fixed_size_keys_pool = key_size_is_fixed ?
+		std::make_unique<SmallObjectPool>(key_size) : nullptr;
+
+	mutable std::mt19937_64 rnd_engine{getSeed()};
+
+	mutable std::size_t bytes_allocated = 0;
+	mutable std::atomic<std::size_t> element_count{0};
+	mutable std::atomic<std::size_t> hit_count{0};
+	mutable std::atomic<std::size_t> query_count{0};
+
+	const std::chrono::time_point<std::chrono::system_clock> creation_time = std::chrono::system_clock::now();
+};
+
+}

dbms/include/DB/Dictionaries/ComplexKeyHashedDictionary.h

@@ -0,0 +1,562 @@
+#pragma once
+
+#include <DB/Dictionaries/IDictionary.h>
+#include <DB/Dictionaries/IDictionarySource.h>
+#include <DB/Dictionaries/DictionaryStructure.h>
+#include <DB/Core/StringRef.h>
+#include <DB/Common/HashTable/HashMap.h>
+#include <DB/Columns/ColumnString.h>
+#include <DB/Common/Arena.h>
+#include <ext/range.hpp>
+#include <atomic>
+#include <memory>
+#include <tuple>
+
+
+namespace DB
+{
+
+class ComplexKeyHashedDictionary final : public IDictionaryBase
+{
+public:
+	ComplexKeyHashedDictionary(
+		const std::string & name, const DictionaryStructure & dict_struct, DictionarySourcePtr source_ptr,
+		const DictionaryLifetime dict_lifetime, bool require_nonempty)
+	: name{name}, dict_struct(dict_struct), source_ptr{std::move(source_ptr)}, dict_lifetime(dict_lifetime),
+	  require_nonempty(require_nonempty), key_description{createKeyDescription(dict_struct)}
+	{
+		createAttributes();
+
+		try
+		{
+			loadData();
+			calculateBytesAllocated();
+		}
+		catch (...)
+		{
+			creation_exception = std::current_exception();
+		}
+
+		creation_time = std::chrono::system_clock::now();
+	}
+
+	ComplexKeyHashedDictionary(const ComplexKeyHashedDictionary & other)
+		: ComplexKeyHashedDictionary{other.name, other.dict_struct, other.source_ptr->clone(), other.dict_lifetime, other.require_nonempty}
+	{}
+
+	std::string getKeyDescription() const { return key_description; };
+
+	std::exception_ptr getCreationException() const override { return creation_exception; }
+
+	std::string getName() const override { return name; }
+
+	std::string getTypeName() const override { return "ComplexKeyHashed"; }
+
+	std::size_t getBytesAllocated() const override { return bytes_allocated; }
+
+	std::size_t getQueryCount() const override { return query_count.load(std::memory_order_relaxed); }
+
+	double getHitRate() const override { return 1.0; }
+
+	std::size_t getElementCount() const override { return element_count; }
+
+	double getLoadFactor() const override { return static_cast<double>(element_count) / bucket_count; }
+
+	bool isCached() const override { return false; }
+
+	DictionaryPtr clone() const override { return std::make_unique<ComplexKeyHashedDictionary>(*this); }
+
+	const IDictionarySource * getSource() const override { return source_ptr.get(); }
+
+	const DictionaryLifetime & getLifetime() const override { return dict_lifetime; }
+
+	const DictionaryStructure & getStructure() const override { return dict_struct; }
+
+	std::chrono::time_point<std::chrono::system_clock> getCreationTime() const override
+	{
+		return creation_time;
+	}
+
+	bool isInjective(const std::string & attribute_name) const override
+	{
+		return dict_struct.attributes[&getAttribute(attribute_name) - attributes.data()].injective;
+	}
+
+#define DECLARE_MULTIPLE_GETTER(TYPE)\
+	void get##TYPE(\
+		const std::string & attribute_name, const ConstColumnPlainPtrs & key_columns, const DataTypes & key_types,\
+		PODArray<TYPE> & out) const\
+	{\
+		validateKeyTypes(key_types);\
+		\
+		const auto & attribute = getAttribute(attribute_name);\
+		if (attribute.type != AttributeUnderlyingType::TYPE)\
+			throw Exception{\
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),\
+				ErrorCodes::TYPE_MISMATCH\
+			};\
+		\
+		const auto null_value = std::get<TYPE>(attribute.null_values);\
+		\
+		getItems<TYPE>(attribute, key_columns,\
+			[&] (const std::size_t row, const auto value) { out[row] = value; },\
+			[&] (const std::size_t) { return null_value; });\
+	}
+	DECLARE_MULTIPLE_GETTER(UInt8)
+	DECLARE_MULTIPLE_GETTER(UInt16)
+	DECLARE_MULTIPLE_GETTER(UInt32)
+	DECLARE_MULTIPLE_GETTER(UInt64)
+	DECLARE_MULTIPLE_GETTER(Int8)
+	DECLARE_MULTIPLE_GETTER(Int16)
+	DECLARE_MULTIPLE_GETTER(Int32)
+	DECLARE_MULTIPLE_GETTER(Int64)
+	DECLARE_MULTIPLE_GETTER(Float32)
+	DECLARE_MULTIPLE_GETTER(Float64)
+#undef DECLARE_MULTIPLE_GETTER
+	void getString(
+		const std::string & attribute_name, const ConstColumnPlainPtrs & key_columns, const DataTypes & key_types,
+		ColumnString * out) const
+	{
+		validateKeyTypes(key_types);
+
+		const auto & attribute = getAttribute(attribute_name);
+		if (attribute.type != AttributeUnderlyingType::String)
+			throw Exception{
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		const auto & null_value = StringRef{std::get<String>(attribute.null_values)};
+
+		getItems<StringRef>(attribute, key_columns,
+			[&] (const std::size_t row, const StringRef value) { out->insertData(value.data, value.size); },
+			[&] (const std::size_t) { return null_value; });
+	}
+
+#define DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(TYPE)\
+	void get##TYPE(\
+		const std::string & attribute_name, const ConstColumnPlainPtrs & key_columns, const DataTypes & key_types,\
+		const PODArray<TYPE> & def, PODArray<TYPE> & out) const\
+	{\
+ 		validateKeyTypes(key_types);\
+ 		\
+		const auto & attribute = getAttribute(attribute_name);\
+		if (attribute.type != AttributeUnderlyingType::TYPE)\
+			throw Exception{\
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),\
+				ErrorCodes::TYPE_MISMATCH\
+			};\
+		\
+		getItems<TYPE>(attribute, key_columns,\
+			[&] (const std::size_t row, const auto value) { out[row] = value; },\
+			[&] (const std::size_t row) { return def[row]; });\
+	}
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt8)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt16)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt64)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int8)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int16)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int64)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Float32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Float64)
+#undef DECLARE_MULTIPLE_GETTER_WITH_DEFAULT
+	void getString(
+		const std::string & attribute_name, const ConstColumnPlainPtrs & key_columns, const DataTypes & key_types,
+		const ColumnString * const def, ColumnString * const out) const
+	{
+ 		validateKeyTypes(key_types);
+
+		const auto & attribute = getAttribute(attribute_name);
+		if (attribute.type != AttributeUnderlyingType::String)
+			throw Exception{
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		getItems<StringRef>(attribute, key_columns,
+			[&] (const std::size_t row, const StringRef value) { out->insertData(value.data, value.size); },
+			[&] (const std::size_t row) { return def->getDataAt(row); });
+	}
+
+	void has(const ConstColumnPlainPtrs & key_columns, const DataTypes & key_types, PODArray<UInt8> & out) const
+	{
+		validateKeyTypes(key_types);
+
+		const auto & attribute = attributes.front();
+
+		switch (attribute.type)
+		{
+			case AttributeUnderlyingType::UInt8: has<UInt8>(attribute, key_columns, out); break;
+			case AttributeUnderlyingType::UInt16: has<UInt16>(attribute, key_columns, out); break;
+			case AttributeUnderlyingType::UInt32: has<UInt32>(attribute, key_columns, out); break;
+			case AttributeUnderlyingType::UInt64: has<UInt64>(attribute, key_columns, out); break;
+			case AttributeUnderlyingType::Int8: has<Int8>(attribute, key_columns, out); break;
+			case AttributeUnderlyingType::Int16: has<Int16>(attribute, key_columns, out); break;
+			case AttributeUnderlyingType::Int32: has<Int32>(attribute, key_columns, out); break;
+			case AttributeUnderlyingType::Int64: has<Int64>(attribute, key_columns, out); break;
+			case AttributeUnderlyingType::Float32: has<Float32>(attribute, key_columns, out); break;
+			case AttributeUnderlyingType::Float64: has<Float64>(attribute, key_columns, out); break;
+			case AttributeUnderlyingType::String: has<StringRef>(attribute, key_columns, out); break;
+		}
+	}
+
+private:
+	template <typename Value> using ContainerType = HashMapWithSavedHash<StringRef, Value, StringRefHash>;
+	template <typename Value> using ContainerPtrType = std::unique_ptr<ContainerType<Value>>;
+
+	struct attribute_t final
+	{
+		AttributeUnderlyingType type;
+		std::tuple<
+			UInt8, UInt16, UInt32, UInt64,
+			Int8, Int16, Int32, Int64,
+			Float32, Float64,
+			String> null_values;
+		std::tuple<
+			ContainerPtrType<UInt8>, ContainerPtrType<UInt16>, ContainerPtrType<UInt32>, ContainerPtrType<UInt64>,
+			ContainerPtrType<Int8>, ContainerPtrType<Int16>, ContainerPtrType<Int32>, ContainerPtrType<Int64>,
+			ContainerPtrType<Float32>, ContainerPtrType<Float64>,
+			ContainerPtrType<StringRef>> maps;
+		std::unique_ptr<Arena> string_arena;
+	};
+
+	void createAttributes()
+	{
+		const auto size = dict_struct.attributes.size();
+		attributes.reserve(size);
+
+		for (const auto & attribute : dict_struct.attributes)
+		{
+			attribute_index_by_name.emplace(attribute.name, attributes.size());
+			attributes.push_back(createAttributeWithType(attribute.underlying_type, attribute.null_value));
+
+			if (attribute.hierarchical)
+				throw Exception{
+					name + ": hierarchical attributes not supported for dictionary of type " + getTypeName(),
+					ErrorCodes::TYPE_MISMATCH
+				};
+		}
+	}
+
+	void loadData()
+	{
+		auto stream = source_ptr->loadAll();
+		stream->readPrefix();
+
+		/// created upfront to avoid excess allocations
+		const auto keys_size = dict_struct.key->size();
+		StringRefs keys(keys_size);
+
+		const auto attributes_size = attributes.size();
+
+		while (const auto block = stream->read())
+		{
+			const auto rows = block.rowsInFirstColumn();
+			element_count += rows;
+
+			const auto key_column_ptrs = ext::map<ConstColumnPlainPtrs>(ext::range(0, keys_size),
+				[&] (const std::size_t attribute_idx) {
+					return block.getByPosition(attribute_idx).column.get();
+				});
+
+			const auto attribute_column_ptrs = ext::map<ConstColumnPlainPtrs>(ext::range(0, attributes_size),
+				[&] (const std::size_t attribute_idx) {
+					return block.getByPosition(keys_size + attribute_idx).column.get();
+				});
+
+			for (const auto row_idx : ext::range(0, rows))
+			{
+				/// calculate key once per row
+				const auto key = placeKeysInPool(row_idx, key_column_ptrs, keys, keys_pool);
+
+				auto should_rollback = false;
+
+				for (const auto attribute_idx : ext::range(0, attributes_size))
+				{
+					const auto & attribute_column = *attribute_column_ptrs[attribute_idx];
+					auto & attribute = attributes[attribute_idx];
+					const auto inserted = setAttributeValue(attribute, key, attribute_column[row_idx]);
+					if (!inserted)
+						should_rollback = true;
+				}
+
+				/// @note on multiple equal keys the mapped value for the first one is stored
+				if (should_rollback)
+					keys_pool.rollback(key.size);
+			}
+
+		}
+
+		stream->readSuffix();
+
+		if (require_nonempty && 0 == element_count)
+			throw Exception{
+				name + ": dictionary source is empty and 'require_nonempty' property is set.",
+				ErrorCodes::DICTIONARY_IS_EMPTY
+			};
+	}
+
+	template <typename T>
+	void addAttributeSize(const attribute_t & attribute)
+	{
+		const auto & map_ref = std::get<ContainerPtrType<T>>(attribute.maps);
+		bytes_allocated += sizeof(ContainerType<T>) + map_ref->getBufferSizeInBytes();
+		bucket_count = map_ref->getBufferSizeInCells();
+	}
+
+	void calculateBytesAllocated()
+	{
+		bytes_allocated += attributes.size() * sizeof(attributes.front());
+
+		for (const auto & attribute : attributes)
+		{
+			switch (attribute.type)
+			{
+				case AttributeUnderlyingType::UInt8: addAttributeSize<UInt8>(attribute); break;
+				case AttributeUnderlyingType::UInt16: addAttributeSize<UInt16>(attribute); break;
+				case AttributeUnderlyingType::UInt32: addAttributeSize<UInt32>(attribute); break;
+				case AttributeUnderlyingType::UInt64: addAttributeSize<UInt64>(attribute); break;
+				case AttributeUnderlyingType::Int8: addAttributeSize<Int8>(attribute); break;
+				case AttributeUnderlyingType::Int16: addAttributeSize<Int16>(attribute); break;
+				case AttributeUnderlyingType::Int32: addAttributeSize<Int32>(attribute); break;
+				case AttributeUnderlyingType::Int64: addAttributeSize<Int64>(attribute); break;
+				case AttributeUnderlyingType::Float32: addAttributeSize<Float32>(attribute); break;
+				case AttributeUnderlyingType::Float64: addAttributeSize<Float64>(attribute); break;
+				case AttributeUnderlyingType::String:
+				{
+					addAttributeSize<StringRef>(attribute);
+					bytes_allocated += sizeof(Arena) + attribute.string_arena->size();
+
+					break;
+				}
+			}
+		}
+
+		bytes_allocated += keys_pool.size();
+	}
+
+	template <typename T>
+	void createAttributeImpl(attribute_t & attribute, const Field & null_value)
+	{
+		std::get<T>(attribute.null_values) = null_value.get<typename NearestFieldType<T>::Type>();
+		std::get<ContainerPtrType<T>>(attribute.maps) = std::make_unique<ContainerType<T>>();
+	}
+
+	attribute_t createAttributeWithType(const AttributeUnderlyingType type, const Field & null_value)
+	{
+		attribute_t attr{type};
+
+		switch (type)
+		{
+			case AttributeUnderlyingType::UInt8: createAttributeImpl<UInt8>(attr, null_value); break;
+			case AttributeUnderlyingType::UInt16: createAttributeImpl<UInt16>(attr, null_value); break;
+			case AttributeUnderlyingType::UInt32: createAttributeImpl<UInt32>(attr, null_value); break;
+			case AttributeUnderlyingType::UInt64: createAttributeImpl<UInt64>(attr, null_value); break;
+			case AttributeUnderlyingType::Int8: createAttributeImpl<Int8>(attr, null_value); break;
+			case AttributeUnderlyingType::Int16: createAttributeImpl<Int16>(attr, null_value); break;
+			case AttributeUnderlyingType::Int32: createAttributeImpl<Int32>(attr, null_value); break;
+			case AttributeUnderlyingType::Int64: createAttributeImpl<Int64>(attr, null_value); break;
+			case AttributeUnderlyingType::Float32: createAttributeImpl<Float32>(attr, null_value); break;
+			case AttributeUnderlyingType::Float64: createAttributeImpl<Float64>(attr, null_value); break;
+			case AttributeUnderlyingType::String:
+			{
+				std::get<String>(attr.null_values) = null_value.get<String>();
+				std::get<ContainerPtrType<StringRef>>(attr.maps) = std::make_unique<ContainerType<StringRef>>();
+				attr.string_arena = std::make_unique<Arena>();
+				break;
+			}
+		}
+
+		return attr;
+	}
+
+	static std::string createKeyDescription(const DictionaryStructure & dict_struct)
+	{
+		std::ostringstream out;
+
+		out << '(';
+
+		auto first = true;
+		for (const auto & key : *dict_struct.key)
+		{
+			if (!first)
+				out << ", ";
+
+			first = false;
+
+			out << key.type->getName();
+		}
+
+		out << ')';
+
+		return out.str();
+	}
+
+	void validateKeyTypes(const DataTypes & key_types) const
+	{
+		if (key_types.size() != dict_struct.key->size())
+			throw Exception{
+				"Key structure does not match, expected " + key_description,
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		for (const auto i : ext::range(0, key_types.size()))
+		{
+			const auto & expected_type = (*dict_struct.key)[i].type->getName();
+			const auto & actual_type = key_types[i]->getName();
+
+			if (expected_type != actual_type)
+				throw Exception{
+					"Key type at position " + std::to_string(i) + " does not match, expected " + expected_type +
+						", found " + actual_type,
+					ErrorCodes::TYPE_MISMATCH
+				};
+		}
+	}
+
+	template <typename T, typename ValueSetter, typename DefaultGetter>
+	void getItems(
+		const attribute_t & attribute, const ConstColumnPlainPtrs & key_columns, ValueSetter && set_value,
+		DefaultGetter && get_default) const
+	{
+		const auto & attr = *std::get<ContainerPtrType<T>>(attribute.maps);
+
+		const auto keys_size = key_columns.size();
+		StringRefs keys(keys_size);
+		Arena temporary_keys_pool;
+
+		const auto rows = key_columns.front()->size();
+		for (const auto i : ext::range(0, rows))
+		{
+			/// copy key data to arena so it is contiguous and return StringRef to it
+			const auto key = placeKeysInPool(i, key_columns, keys, temporary_keys_pool);
+
+			const auto it = attr.find(key);
+			set_value(i, it != attr.end() ? it->second : get_default(i));
+
+			/// free memory allocated for the key
+			temporary_keys_pool.rollback(key.size);
+		}
+
+		query_count.fetch_add(rows, std::memory_order_relaxed);
+	}
+
+	template <typename T>
+	bool setAttributeValueImpl(attribute_t & attribute, const StringRef key, const T value)
+	{
+		auto & map = *std::get<ContainerPtrType<T>>(attribute.maps);
+		const auto pair = map.insert({ key, value });
+		return pair.second;
+	}
+
+	bool setAttributeValue(attribute_t & attribute, const StringRef key, const Field & value)
+	{
+		switch (attribute.type)
+		{
+			case AttributeUnderlyingType::UInt8: return setAttributeValueImpl<UInt8>(attribute, key, value.get<UInt64>());
+			case AttributeUnderlyingType::UInt16: return setAttributeValueImpl<UInt16>(attribute, key, value.get<UInt64>());
+			case AttributeUnderlyingType::UInt32: return setAttributeValueImpl<UInt32>(attribute, key, value.get<UInt64>());
+			case AttributeUnderlyingType::UInt64: return setAttributeValueImpl<UInt64>(attribute, key, value.get<UInt64>());
+			case AttributeUnderlyingType::Int8: return setAttributeValueImpl<Int8>(attribute, key, value.get<Int64>());
+			case AttributeUnderlyingType::Int16: return setAttributeValueImpl<Int16>(attribute, key, value.get<Int64>());
+			case AttributeUnderlyingType::Int32: return setAttributeValueImpl<Int32>(attribute, key, value.get<Int64>());
+			case AttributeUnderlyingType::Int64: return setAttributeValueImpl<Int64>(attribute, key, value.get<Int64>());
+			case AttributeUnderlyingType::Float32: return setAttributeValueImpl<Float32>(attribute, key, value.get<Float64>());
+			case AttributeUnderlyingType::Float64: return setAttributeValueImpl<Float64>(attribute, key, value.get<Float64>());
+			case AttributeUnderlyingType::String:
+			{
+				auto & map = *std::get<ContainerPtrType<StringRef>>(attribute.maps);
+				const auto & string = value.get<String>();
+				const auto string_in_arena = attribute.string_arena->insert(string.data(), string.size());
+				const auto pair = map.insert({ key, StringRef{string_in_arena, string.size()} });
+				return pair.second;
+			}
+		}
+
+		return {};
+	}
+
+	const attribute_t & getAttribute(const std::string & attribute_name) const
+	{
+		const auto it = attribute_index_by_name.find(attribute_name);
+		if (it == std::end(attribute_index_by_name))
+			throw Exception{
+				name + ": no such attribute '" + attribute_name + "'",
+				ErrorCodes::BAD_ARGUMENTS
+			};
+
+		return attributes[it->second];
+	}
+
+	static StringRef placeKeysInPool(
+		const std::size_t row, const ConstColumnPlainPtrs & key_columns, StringRefs & keys, Arena & pool)
+	{
+		const auto keys_size = key_columns.size();
+		size_t sum_keys_size{};
+		for (const auto i : ext::range(0, keys_size))
+		{
+			keys[i] = key_columns[i]->getDataAtWithTerminatingZero(row);
+			sum_keys_size += keys[i].size;
+		}
+
+		const auto res = pool.alloc(sum_keys_size);
+		auto place = res;
+
+		for (size_t j = 0; j < keys_size; ++j)
+		{
+			memcpy(place, keys[j].data, keys[j].size);
+			place += keys[j].size;
+		}
+
+		return { res, sum_keys_size };
+	}
+
+	template <typename T>
+	void has(const attribute_t & attribute, const ConstColumnPlainPtrs & key_columns, PODArray<UInt8> & out) const
+	{
+		const auto & attr = *std::get<ContainerPtrType<T>>(attribute.maps);
+		const auto keys_size = key_columns.size();
+		StringRefs keys(keys_size);
+		Arena temporary_keys_pool;
+		const auto rows = key_columns.front()->size();
+
+		for (const auto i : ext::range(0, rows))
+		{
+			/// copy key data to arena so it is contiguous and return StringRef to it
+			const auto key = placeKeysInPool(i, key_columns, keys, temporary_keys_pool);
+
+			const auto it = attr.find(key);
+			out[i] = it != attr.end();
+
+			/// free memory allocated for the key
+			temporary_keys_pool.rollback(key.size);
+		}
+
+		query_count.fetch_add(rows, std::memory_order_relaxed);
+	}
+
+	const std::string name;
+	const DictionaryStructure dict_struct;
+	const DictionarySourcePtr source_ptr;
+	const DictionaryLifetime dict_lifetime;
+	const bool require_nonempty;
+	const std::string key_description;
+
+	std::map<std::string, std::size_t> attribute_index_by_name;
+	std::vector<attribute_t> attributes;
+	Arena keys_pool;
+
+	std::size_t bytes_allocated = 0;
+	std::size_t element_count = 0;
+	std::size_t bucket_count = 0;
+	mutable std::atomic<std::size_t> query_count{0};
+
+	std::chrono::time_point<std::chrono::system_clock> creation_time;
+
+	std::exception_ptr creation_exception;
+};
+
+
+}

dbms/include/DB/Dictionaries/DictionarySourceFactory.h

@@ -20,14 +20,29 @@ namespace
 
 Block createSampleBlock(const DictionaryStructure & dict_struct)
 {
-	Block block{
-		ColumnWithTypeAndName{new ColumnUInt64{1}, new DataTypeUInt64, dict_struct.id.name}
-	};
+	Block block;
+
+	if (dict_struct.id)
+		block.insert(ColumnWithTypeAndName{
+			new ColumnUInt64{1}, new DataTypeUInt64, dict_struct.id->name
+		});
+
+	if (dict_struct.key)
+	{
+		for (const auto & attribute : *dict_struct.key)
+		{
+			auto column = attribute.type->createColumn();
+			column->insertDefault();
+
+			block.insert(ColumnWithTypeAndName{column, attribute.type, attribute.name});
+		}
+	}
 
 	if (dict_struct.range_min)
 		for (const auto & attribute : { dict_struct.range_min, dict_struct.range_max })
-			block.insert(
-				ColumnWithTypeAndName{new ColumnUInt16{1}, new DataTypeDate, attribute->name});
+			block.insert(ColumnWithTypeAndName{
+				new ColumnUInt16{1}, new DataTypeDate, attribute->name
+			});
 
 	for (const auto & attribute : dict_struct.attributes)
 	{

dbms/include/DB/Dictionaries/DictionaryStructure.h

@@ -136,20 +136,36 @@ struct DictionarySpecialAttribute final
 /// Name of identifier plus list of attributes
 struct DictionaryStructure final
 {
-	DictionarySpecialAttribute id;
+	std::experimental::optional<DictionarySpecialAttribute> id;
+	std::experimental::optional<std::vector<DictionaryAttribute>> key;
 	std::vector<DictionaryAttribute> attributes;
 	std::experimental::optional<DictionarySpecialAttribute> range_min;
 	std::experimental::optional<DictionarySpecialAttribute> range_max;
 	bool has_expressions = false;
 
 	DictionaryStructure(const Poco::Util::AbstractConfiguration & config, const std::string & config_prefix)
-		: id{config, config_prefix + ".id"}
 	{
-		if (id.name.empty())
-			throw Exception{
-				"No 'id' specified for dictionary",
-				ErrorCodes::BAD_ARGUMENTS
-			};
+		const auto has_id = config.has(config_prefix + ".id");
+		const auto has_key = config.has(config_prefix + ".key");
+
+		if (has_key && has_id)
+			throw Exception{"Only one of 'id' and 'key' should be specified", ErrorCodes::BAD_ARGUMENTS};
+
+		if (has_id)
+			id.emplace(config, config_prefix + ".id");
+		else if (has_key)
+		{
+			key.emplace(getAttributes(config, config_prefix + ".key", false, false));
+			if (key->empty())
+				throw Exception{"Empty 'key' supplied", ErrorCodes::BAD_ARGUMENTS};
+		}
+		else
+			throw Exception{"Dictionary structure should specify either 'id' or 'key'", ErrorCodes::BAD_ARGUMENTS};
+
+		if (id)
+		{
+			if (id->name.empty())
+				throw Exception{"'id' cannot be empty", ErrorCodes::BAD_ARGUMENTS};
 
 			if (config.has(config_prefix + ".range_min"))
 				range_min.emplace(config, config_prefix + ".range_min");
@@ -157,14 +173,46 @@ struct DictionaryStructure final
 			if (config.has(config_prefix + ".range_max"))
 				range_max.emplace(config, config_prefix + ".range_max");
 
-		if (!id.expression.empty() ||
-			(range_min && !range_min->expression.empty()) || (range_max && !range_max->expression.empty()))
+			if (!id->expression.empty() ||
+				(range_min && !range_min->expression.empty()) ||
+				(range_max && !range_max->expression.empty()))
 				has_expressions = true;
+		}
 
+		attributes = getAttributes(config, config_prefix);
+		if (attributes.empty())
+			throw Exception{"Dictionary has no attributes defined", ErrorCodes::BAD_ARGUMENTS};
+	}
+
+	bool isKeySizeFixed() const
+	{
+		if (!key)
+			return true;
+
+		for (const auto key_i : * key)
+			if (key_i.underlying_type == AttributeUnderlyingType::String)
+				return false;
+
+		return true;
+	}
+
+	std::size_t getKeySize() const
+	{
+		return std::accumulate(std::begin(*key), std::end(*key), std::size_t{},
+			[] (const auto running_size, const auto & key_i) {return running_size + key_i.type->getSizeOfField(); });
+	}
+
+private:
+	std::vector<DictionaryAttribute> getAttributes(
+		const Poco::Util::AbstractConfiguration & config, const std::string & config_prefix,
+		const bool hierarchy_allowed = true, const bool allow_null_values = true)
+	{
 		Poco::Util::AbstractConfiguration::Keys keys;
 		config.keys(config_prefix, keys);
 		auto has_hierarchy = false;
 
+		std::vector<DictionaryAttribute> attributes;
+
 		for (const auto & key : keys)
 		{
 			if (0 != strncmp(key.data(), "attribute", strlen("attribute")))
@@ -181,8 +229,10 @@ struct DictionaryStructure final
 			if (!expression.empty())
 				has_expressions = true;
 
-			const auto null_value_string = config.getString(prefix + "null_value");
 			Field null_value;
+			if (allow_null_values)
+			{
+				const auto null_value_string = config.getString(prefix + "null_value");
 				try
 				{
 					ReadBufferFromString null_value_buffer{null_value_string};
@@ -195,6 +245,7 @@ struct DictionaryStructure final
 						ErrorCodes::BAD_ARGUMENTS
 					};
 				}
+			}
 
 			const auto hierarchical = config.getBool(prefix + "hierarchical", false);
 			const auto injective = config.getBool(prefix + "injective", false);
@@ -204,6 +255,12 @@ struct DictionaryStructure final
 					ErrorCodes::BAD_ARGUMENTS
 				};
 
+			if (has_hierarchy && !hierarchy_allowed)
+				throw Exception{
+					"Hierarchy not allowed in '" + prefix,
+					ErrorCodes::BAD_ARGUMENTS
+				};
+
 			if (has_hierarchy && hierarchical)
 				throw Exception{
 					"Only one hierarchical attribute supported",
@@ -217,11 +274,7 @@ struct DictionaryStructure final
 			});
 		}
 
-		if (attributes.empty())
-			throw Exception{
-				"Dictionary has no attributes defined",
-				ErrorCodes::BAD_ARGUMENTS
-			};
+		return attributes;
 	}
 };
 

dbms/include/DB/Dictionaries/FileDictionarySource.h

@@ -41,10 +41,13 @@ public:
 
 	BlockInputStreamPtr loadIds(const std::vector<std::uint64_t> & ids) override
 	{
-		throw Exception{
-			"Method unsupported",
-			ErrorCodes::NOT_IMPLEMENTED
-		};
+		throw Exception{"Method unsupported", ErrorCodes::NOT_IMPLEMENTED};
+	}
+
+	BlockInputStreamPtr loadKeys(
+		const ConstColumnPlainPtrs & key_columns, const std::vector<std::size_t> & requested_rows) override
+	{
+		throw Exception{"Method unsupported", ErrorCodes::NOT_IMPLEMENTED};
 	}
 
 	bool isModified() const override { return getLastModification() > last_modification; }

dbms/include/DB/Dictionaries/FlatDictionary.h

@@ -6,10 +6,12 @@
 #include <DB/Columns/ColumnString.h>
 #include <DB/Common/Arena.h>
 #include <ext/range.hpp>
+#include <ext/size.hpp>
 #include <atomic>
 #include <vector>
 #include <tuple>
 
+
 namespace DB
 {
 
@@ -84,7 +86,11 @@ public:
 
 	void toParent(const PODArray<id_t> & ids, PODArray<id_t> & out) const override
 	{
-		getItems<UInt64>(*hierarchical_attribute, ids, out);
+		const auto null_value = std::get<UInt64>(hierarchical_attribute->null_values);
+
+		getItems<UInt64>(*hierarchical_attribute, ids,
+			[&] (const std::size_t row, const UInt64 value) { out[row] = value; },
+			[&] (const std::size_t) { return null_value; });
 	}
 
 #define DECLARE_MULTIPLE_GETTER(TYPE)\
@@ -97,7 +103,11 @@ public:
 				ErrorCodes::TYPE_MISMATCH\
 			};\
 		\
-		getItems<TYPE>(attribute, ids, out);\
+		const auto null_value = std::get<TYPE>(attribute.null_values);\
+		\
+		getItems<TYPE>(attribute, ids,\
+			[&] (const std::size_t row, const auto value) { out[row] = value; },\
+			[&] (const std::size_t) { return null_value; });\
 	}
 	DECLARE_MULTIPLE_GETTER(UInt8)
 	DECLARE_MULTIPLE_GETTER(UInt16)
@@ -119,38 +129,93 @@ public:
 				ErrorCodes::TYPE_MISMATCH
 			};
 
-		const auto & attr = *std::get<std::unique_ptr<PODArray<StringRef>>>(attribute.arrays);
-		const auto & null_value = std::get<String>(attribute.null_values);
+		const auto & null_value = StringRef{std::get<String>(attribute.null_values)};
 
-		for (const auto i : ext::range(0, ids.size()))
-		{
-			const auto id = ids[i];
-			const auto string_ref = id < attr.size() ? attr[id] : StringRef{null_value};
-			out->insertData(string_ref.data, string_ref.size);
+		getItems<StringRef>(attribute, ids,
+			[&] (const std::size_t row, const StringRef value) { out->insertData(value.data, value.size); },
+			[&] (const std::size_t) { return null_value; });
 	}
 
-		query_count.fetch_add(ids.size(), std::memory_order_relaxed);
+#define DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(TYPE)\
+	void get##TYPE(\
+		const std::string & attribute_name, const PODArray<id_t> & ids, const PODArray<TYPE> & def,\
+		PODArray<TYPE> & out) const override\
+	{\
+		const auto & attribute = getAttribute(attribute_name);\
+		if (attribute.type != AttributeUnderlyingType::TYPE)\
+			throw Exception{\
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),\
+				ErrorCodes::TYPE_MISMATCH\
+			};\
+		\
+		getItems<TYPE>(attribute, ids,\
+			[&] (const std::size_t row, const auto value) { out[row] = value; },\
+			[&] (const std::size_t row) { return def[row]; });\
+	}
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt8)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt16)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt64)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int8)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int16)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int64)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Float32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Float64)
+#undef DECLARE_MULTIPLE_GETTER_WITH_DEFAULT
+	void getString(
+		const std::string & attribute_name, const PODArray<id_t> & ids, const ColumnString * const def,
+		ColumnString * const out) const override
+	{
+		const auto & attribute = getAttribute(attribute_name);
+		if (attribute.type != AttributeUnderlyingType::String)
+			throw Exception{
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		getItems<StringRef>(attribute, ids,
+			[&] (const std::size_t row, const StringRef value) { out->insertData(value.data, value.size); },
+			[&] (const std::size_t row) { return def->getDataAt(row); });
+	}
+
+	void has(const PODArray<id_t> & ids, PODArray<UInt8> & out) const override
+	{
+		const auto & attribute = attributes.front();
+
+		switch (attribute.type)
+		{
+			case AttributeUnderlyingType::UInt8: has<UInt8>(attribute, ids, out); break;
+			case AttributeUnderlyingType::UInt16: has<UInt16>(attribute, ids, out); break;
+			case AttributeUnderlyingType::UInt32: has<UInt32>(attribute, ids, out); break;
+			case AttributeUnderlyingType::UInt64: has<UInt64>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Int8: has<Int8>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Int16: has<Int16>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Int32: has<Int32>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Int64: has<Int64>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Float32: has<Float32>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Float64: has<Float64>(attribute, ids, out); break;
+			case AttributeUnderlyingType::String: has<String>(attribute, ids, out); break;
+		}
 	}
 
 private:
+	template <typename Value> using ContainerType = PODArray<Value>;
+	template <typename Value> using ContainerPtrType = std::unique_ptr<ContainerType<Value>>;
+
 	struct attribute_t final
 	{
 		AttributeUnderlyingType type;
-		std::tuple<UInt8, UInt16, UInt32, UInt64,
+		std::tuple<
+			UInt8, UInt16, UInt32, UInt64,
 			Int8, Int16, Int32, Int64,
 			Float32, Float64,
 			String> null_values;
-		std::tuple<std::unique_ptr<PODArray<UInt8>>,
-			std::unique_ptr<PODArray<UInt16>>,
-			std::unique_ptr<PODArray<UInt32>>,
-			std::unique_ptr<PODArray<UInt64>>,
-			std::unique_ptr<PODArray<Int8>>,
-			std::unique_ptr<PODArray<Int16>>,
-			std::unique_ptr<PODArray<Int32>>,
-			std::unique_ptr<PODArray<Int64>>,
-			std::unique_ptr<PODArray<Float32>>,
-			std::unique_ptr<PODArray<Float64>>,
-			std::unique_ptr<PODArray<StringRef>>> arrays;
+		std::tuple<
+			ContainerPtrType<UInt8>, ContainerPtrType<UInt16>, ContainerPtrType<UInt32>, ContainerPtrType<UInt64>,
+			ContainerPtrType<Int8>, ContainerPtrType<Int16>, ContainerPtrType<Int32>, ContainerPtrType<Int64>,
+			ContainerPtrType<Float32>, ContainerPtrType<Float64>,
+			ContainerPtrType<StringRef>> arrays;
 		std::unique_ptr<Arena> string_arena;
 	};
 
@@ -210,7 +275,7 @@ private:
 	template <typename T>
 	void addAttributeSize(const attribute_t & attribute)
 	{
-		const auto & array_ref = std::get<std::unique_ptr<PODArray<T>>>(attribute.arrays);
+		const auto & array_ref = std::get<ContainerPtrType<T>>(attribute.arrays);
 		bytes_allocated += sizeof(PODArray<T>) + array_ref->storage_size();
 		bucket_count = array_ref->capacity();
 	}
@@ -249,8 +314,8 @@ private:
 	{
 		const auto & null_value_ref = std::get<T>(attribute.null_values) =
 			null_value.get<typename NearestFieldType<T>::Type>();
-		std::get<std::unique_ptr<PODArray<T>>>(attribute.arrays) =
-			std::make_unique<PODArray<T>>(initial_array_size, null_value_ref);
+		std::get<ContainerPtrType<T>>(attribute.arrays) =
+			std::make_unique<ContainerType<T>>(initial_array_size, null_value_ref);
 	}
 
 	attribute_t createAttributeWithType(const AttributeUnderlyingType type, const Field & null_value)
@@ -272,8 +337,8 @@ private:
 			case AttributeUnderlyingType::String:
 			{
 				const auto & null_value_ref = std::get<String>(attr.null_values) = null_value.get<String>();
-				std::get<std::unique_ptr<PODArray<StringRef>>>(attr.arrays) =
-					std::make_unique<PODArray<StringRef>>(initial_array_size, null_value_ref);
+				std::get<ContainerPtrType<StringRef>>(attr.arrays) =
+					std::make_unique<ContainerType<StringRef>>(initial_array_size, StringRef{null_value_ref});
 				attr.string_arena = std::make_unique<Arena>();
 				break;
 			}
@@ -282,25 +347,27 @@ private:
 		return attr;
 	}
 
-	template <typename T>
-	void getItems(const attribute_t & attribute, const PODArray<id_t> & ids, PODArray<T> & out) const
+	template <typename T, typename ValueSetter, typename DefaultGetter>
+	void getItems(
+		const attribute_t & attribute, const PODArray<id_t> & ids, ValueSetter && set_value,
+		DefaultGetter && get_default) const
 	{
-		const auto & attr = *std::get<std::unique_ptr<PODArray<T>>>(attribute.arrays);
-		const auto null_value = std::get<T>(attribute.null_values);
+		const auto & attr = *std::get<ContainerPtrType<T>>(attribute.arrays);
+		const auto rows = ext::size(ids);
 
-		for (const auto i : ext::range(0, ids.size()))
+		for (const auto i : ext::range(0, rows))
 		{
 			const auto id = ids[i];
-			out[i] = id < attr.size() ? attr[id] : null_value;
+			set_value(i, id < attr.size() ? attr[id] : get_default(i));
 		}
 
-		query_count.fetch_add(ids.size(), std::memory_order_relaxed);
+		query_count.fetch_add(rows, std::memory_order_relaxed);
 	}
 
 	template <typename T>
 	void setAttributeValueImpl(attribute_t & attribute, const id_t id, const T value)
 	{
-		auto & array = *std::get<std::unique_ptr<PODArray<T>>>(attribute.arrays);
+		auto & array = *std::get<ContainerPtrType<T>>(attribute.arrays);
 		if (id >= array.size())
 			array.resize_fill(id + 1, std::get<T>(attribute.null_values));
 		array[id] = value;
@@ -328,9 +395,9 @@ private:
 			case AttributeUnderlyingType::Float64: setAttributeValueImpl<Float64>(attribute, id, value.get<Float64>()); break;
 			case AttributeUnderlyingType::String:
 			{
-				auto & array = *std::get<std::unique_ptr<PODArray<StringRef>>>(attribute.arrays);
+				auto & array = *std::get<ContainerPtrType<StringRef>>(attribute.arrays);
 				if (id >= array.size())
-					array.resize_fill(id + 1, std::get<String>(attribute.null_values));
+					array.resize_fill(id + 1, StringRef{std::get<String>(attribute.null_values)});
 				const auto & string = value.get<String>();
 				const auto string_in_arena = attribute.string_arena->insert(string.data(), string.size());
 				array[id] = StringRef{string_in_arena, string.size()};
@@ -351,6 +418,23 @@ private:
 		return attributes[it->second];
 	}
 
+	template <typename T>
+	void has(const attribute_t & attribute, const PODArray<id_t> & ids, PODArray<UInt8> & out) const
+	{
+		using stored_type = std::conditional_t<std::is_same<T, String>::value, StringRef, T>;
+		const auto & attr = *std::get<ContainerPtrType<stored_type>>(attribute.arrays);
+		const auto & null_value = std::get<T>(attribute.null_values);
+		const auto rows = ext::size(ids);
+
+		for (const auto i : ext::range(0, rows))
+		{
+			const auto id = ids[i];
+			out[i] = id < ext::size(attr) && attr[id] != null_value;
+		}
+
+		query_count.fetch_add(rows, std::memory_order_relaxed);
+	}
+
 	const std::string name;
 	const DictionaryStructure dict_struct;
 	const DictionarySourcePtr source_ptr;

dbms/include/DB/Dictionaries/HashedDictionary.h

@@ -19,8 +19,7 @@ class HashedDictionary final : public IDictionary
 public:
 	HashedDictionary(const std::string & name, const DictionaryStructure & dict_struct,
 		DictionarySourcePtr source_ptr, const DictionaryLifetime dict_lifetime, bool require_nonempty)
-		: name{name}, dict_struct(dict_struct),
-		  source_ptr{std::move(source_ptr)}, dict_lifetime(dict_lifetime),
+		: name{name}, dict_struct(dict_struct), source_ptr{std::move(source_ptr)}, dict_lifetime(dict_lifetime),
 		  require_nonempty(require_nonempty)
 	{
 		createAttributes();
@@ -82,7 +81,11 @@ public:
 
 	void toParent(const PODArray<id_t> & ids, PODArray<id_t> & out) const override
 	{
-		getItems<UInt64>(*hierarchical_attribute, ids, out);
+		const auto null_value = std::get<UInt64>(hierarchical_attribute->null_values);
+
+		getItems<UInt64>(*hierarchical_attribute, ids,
+			[&] (const std::size_t row, const UInt64 value) { out[row] = value; },
+			[&] (const std::size_t) { return null_value; });
 	}
 
 #define DECLARE_MULTIPLE_GETTER(TYPE)\
@@ -95,7 +98,11 @@ public:
 				ErrorCodes::TYPE_MISMATCH\
 			};\
 		\
-		getItems<TYPE>(attribute, ids, out);\
+		const auto null_value = std::get<TYPE>(attribute.null_values);\
+		\
+		getItems<TYPE>(attribute, ids,\
+			[&] (const std::size_t row, const auto value) { out[row] = value; },\
+			[&] (const std::size_t) { return null_value; });\
 	}
 	DECLARE_MULTIPLE_GETTER(UInt8)
 	DECLARE_MULTIPLE_GETTER(UInt16)
@@ -117,38 +124,93 @@ public:
 				ErrorCodes::TYPE_MISMATCH
 			};
 
-		const auto & attr = *std::get<std::unique_ptr<HashMap<UInt64, StringRef>>>(attribute.maps);
-		const auto & null_value = std::get<String>(attribute.null_values);
+		const auto & null_value = StringRef{std::get<String>(attribute.null_values)};
 
-		for (const auto i : ext::range(0, ids.size()))
-		{
-			const auto it = attr.find(ids[i]);
-			const auto string_ref = it != attr.end() ? it->second : StringRef{null_value};
-			out->insertData(string_ref.data, string_ref.size);
+		getItems<StringRef>(attribute, ids,
+			[&] (const std::size_t row, const StringRef value) { out->insertData(value.data, value.size); },
+			[&] (const std::size_t) { return null_value; });
 	}
 
-		query_count.fetch_add(ids.size(), std::memory_order_relaxed);
+#define DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(TYPE)\
+	void get##TYPE(\
+		const std::string & attribute_name, const PODArray<id_t> & ids, const PODArray<TYPE> & def,\
+		PODArray<TYPE> & out) const override\
+	{\
+		const auto & attribute = getAttribute(attribute_name);\
+		if (attribute.type != AttributeUnderlyingType::TYPE)\
+			throw Exception{\
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),\
+				ErrorCodes::TYPE_MISMATCH\
+			};\
+		\
+		getItems<TYPE>(attribute, ids,\
+			[&] (const std::size_t row, const auto value) { out[row] = value; },\
+			[&] (const std::size_t row) { return def[row]; });\
+	}
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt8)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt16)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(UInt64)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int8)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int16)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Int64)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Float32)
+	DECLARE_MULTIPLE_GETTER_WITH_DEFAULT(Float64)
+#undef DECLARE_MULTIPLE_GETTER_WITH_DEFAULT
+	void getString(
+		const std::string & attribute_name, const PODArray<id_t> & ids, const ColumnString * const def,
+		ColumnString * const out) const override
+	{
+		const auto & attribute = getAttribute(attribute_name);
+		if (attribute.type != AttributeUnderlyingType::String)
+			throw Exception{
+				name + ": type mismatch: attribute " + attribute_name + " has type " + toString(attribute.type),
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		getItems<StringRef>(attribute, ids,
+			[&] (const std::size_t row, const StringRef value) { out->insertData(value.data, value.size); },
+			[&] (const std::size_t row) { return def->getDataAt(row); });
+	}
+
+	void has(const PODArray<id_t> & ids, PODArray<UInt8> & out) const override
+	{
+		const auto & attribute = attributes.front();
+
+		switch (attribute.type)
+		{
+			case AttributeUnderlyingType::UInt8: has<UInt8>(attribute, ids, out); break;
+			case AttributeUnderlyingType::UInt16: has<UInt16>(attribute, ids, out); break;
+			case AttributeUnderlyingType::UInt32: has<UInt32>(attribute, ids, out); break;
+			case AttributeUnderlyingType::UInt64: has<UInt64>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Int8: has<Int8>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Int16: has<Int16>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Int32: has<Int32>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Int64: has<Int64>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Float32: has<Float32>(attribute, ids, out); break;
+			case AttributeUnderlyingType::Float64: has<Float64>(attribute, ids, out); break;
+			case AttributeUnderlyingType::String: has<StringRef>(attribute, ids, out); break;
+		}
 	}
 
 private:
+	template <typename Value> using CollectionType = HashMap<UInt64, Value>;
+	template <typename Value> using CollectionPtrType = std::unique_ptr<CollectionType<Value>>;
+
 	struct attribute_t final
 	{
 		AttributeUnderlyingType type;
-		std::tuple<UInt8, UInt16, UInt32, UInt64,
+		std::tuple<
+			UInt8, UInt16, UInt32, UInt64,
 			Int8, Int16, Int32, Int64,
 			Float32, Float64,
 			String> null_values;
-		std::tuple<std::unique_ptr<HashMap<UInt64, UInt8>>,
-			std::unique_ptr<HashMap<UInt64, UInt16>>,
-			std::unique_ptr<HashMap<UInt64, UInt32>>,
-			std::unique_ptr<HashMap<UInt64, UInt64>>,
-			std::unique_ptr<HashMap<UInt64, Int8>>,
-			std::unique_ptr<HashMap<UInt64, Int16>>,
-			std::unique_ptr<HashMap<UInt64, Int32>>,
-			std::unique_ptr<HashMap<UInt64, Int64>>,
-			std::unique_ptr<HashMap<UInt64, Float32>>,
-			std::unique_ptr<HashMap<UInt64, Float64>>,
-			std::unique_ptr<HashMap<UInt64, StringRef>>> maps;
+		std::tuple<
+			CollectionPtrType<UInt8>, CollectionPtrType<UInt16>, CollectionPtrType<UInt32>, CollectionPtrType<UInt64>,
+			CollectionPtrType<Int8>, CollectionPtrType<Int16>, CollectionPtrType<Int32>, CollectionPtrType<Int64>,
+			CollectionPtrType<Float32>, CollectionPtrType<Float64>,
+			CollectionPtrType<StringRef>> maps;
 		std::unique_ptr<Arena> string_arena;
 	};
 
@@ -208,8 +270,8 @@ private:
 	template <typename T>
 	void addAttributeSize(const attribute_t & attribute)
 	{
-		const auto & map_ref = std::get<std::unique_ptr<HashMap<UInt64, T>>>(attribute.maps);
-		bytes_allocated += sizeof(HashMap<UInt64, T>) + map_ref->getBufferSizeInBytes();
+		const auto & map_ref = std::get<CollectionPtrType<T>>(attribute.maps);
+		bytes_allocated += sizeof(CollectionType<T>) + map_ref->getBufferSizeInBytes();
 		bucket_count = map_ref->getBufferSizeInCells();
 	}
 
@@ -246,7 +308,7 @@ private:
 	void createAttributeImpl(attribute_t & attribute, const Field & null_value)
 	{
 		std::get<T>(attribute.null_values) = null_value.get<typename NearestFieldType<T>::Type>();
-		std::get<std::unique_ptr<HashMap<UInt64, T>>>(attribute.maps) = std::make_unique<HashMap<UInt64, T>>();
+		std::get<CollectionPtrType<T>>(attribute.maps) = std::make_unique<CollectionType<T>>();
 	}
 
 	attribute_t createAttributeWithType(const AttributeUnderlyingType type, const Field & null_value)
@@ -268,8 +330,7 @@ private:
 			case AttributeUnderlyingType::String:
 			{
 				std::get<String>(attr.null_values) = null_value.get<String>();
-				std::get<std::unique_ptr<HashMap<UInt64, StringRef>>>(attr.maps) =
-					std::make_unique<HashMap<UInt64, StringRef>>();
+				std::get<CollectionPtrType<StringRef>>(attr.maps) = std::make_unique<CollectionType<StringRef>>();
 				attr.string_arena = std::make_unique<Arena>();
 				break;
 			}
@@ -278,25 +339,27 @@ private:
 		return attr;
 	}
 
-	template <typename T>
-	void getItems(const attribute_t & attribute, const PODArray<id_t> & ids, PODArray<T> & out) const
+	template <typename T, typename ValueSetter, typename DefaultGetter>
+	void getItems(
+		const attribute_t & attribute, const PODArray<id_t> & ids, ValueSetter && set_value,
+		DefaultGetter && get_default) const
 	{
-		const auto & attr = *std::get<std::unique_ptr<HashMap<UInt64, T>>>(attribute.maps);
-		const auto null_value = std::get<T>(attribute.null_values);
+		const auto & attr = *std::get<CollectionPtrType<T>>(attribute.maps);
+		const auto rows = ext::size(ids);
 
-		for (const auto i : ext::range(0, ids.size()))
+		for (const auto i : ext::range(0, rows))
 		{
 			const auto it = attr.find(ids[i]);
-			out[i] = it != attr.end() ? it->second : null_value;
+			set_value(i, it != attr.end() ? it->second : get_default(i));
 		}
 
-		query_count.fetch_add(ids.size(), std::memory_order_relaxed);
+		query_count.fetch_add(rows, std::memory_order_relaxed);
 	}
 
 	template <typename T>
 	void setAttributeValueImpl(attribute_t & attribute, const id_t id, const T value)
 	{
-		auto & map = *std::get<std::unique_ptr<HashMap<UInt64, T>>>(attribute.maps);
+		auto & map = *std::get<CollectionPtrType<T>>(attribute.maps);
 		map.insert({ id, value });
 	}
 
@@ -316,7 +379,7 @@ private:
 			case AttributeUnderlyingType::Float64: setAttributeValueImpl<Float64>(attribute, id, value.get<Float64>()); break;
 			case AttributeUnderlyingType::String:
 			{
-				auto & map = *std::get<std::unique_ptr<HashMap<UInt64, StringRef>>>(attribute.maps);
+				auto & map = *std::get<CollectionPtrType<StringRef>>(attribute.maps);
 				const auto & string = value.get<String>();
 				const auto string_in_arena = attribute.string_arena->insert(string.data(), string.size());
 				map.insert({ id, StringRef{string_in_arena, string.size()} });
@@ -337,6 +400,18 @@ private:
 		return attributes[it->second];
 	}
 
+	template <typename T>
+	void has(const attribute_t & attribute, const PODArray<id_t> & ids, PODArray<UInt8> & out) const
+	{
+		const auto & attr = *std::get<CollectionPtrType<T>>(attribute.maps);
+		const auto rows = ext::size(ids);
+
+		for (const auto i : ext::range(0, rows))
+			out[i] = attr.find(ids[i]) != std::end(attr);
+
+		query_count.fetch_add(rows, std::memory_order_relaxed);
+	}
+
 	const std::string name;
 	const DictionaryStructure dict_struct;
 	const DictionarySourcePtr source_ptr;

dbms/include/DB/Dictionaries/IDictionary.h

@@ -92,6 +92,21 @@ struct IDictionary : IDictionaryBase
 	virtual void getFloat32(const std::string & attr_name, const PODArray<id_t> & ids, PODArray<Float32> & out) const = 0;
 	virtual void getFloat64(const std::string & attr_name, const PODArray<id_t> & ids, PODArray<Float64> & out) const = 0;
 	virtual void getString(const std::string & attr_name, const PODArray<id_t> & ids, ColumnString * out) const = 0;
+
+	/// return mapped values for a collection of identifiers with explicit default values
+	virtual void getUInt8(const std::string & attr_name, const PODArray<id_t> & ids, const PODArray<UInt8> & def, PODArray<UInt8> & out) const = 0;
+	virtual void getUInt16(const std::string & attr_name, const PODArray<id_t> & ids, const PODArray<UInt16> & def, PODArray<UInt16> & out) const = 0;
+	virtual void getUInt32(const std::string & attr_name, const PODArray<id_t> & ids, const PODArray<UInt32> & def, PODArray<UInt32> & out) const = 0;
+	virtual void getUInt64(const std::string & attr_name, const PODArray<id_t> & ids, const PODArray<UInt64> & def, PODArray<UInt64> & out) const = 0;
+	virtual void getInt8(const std::string & attr_name, const PODArray<id_t> & ids, const PODArray<Int8> & def, PODArray<Int8> & out) const = 0;
+	virtual void getInt16(const std::string & attr_name, const PODArray<id_t> & ids, const PODArray<Int16> & def, PODArray<Int16> & out) const = 0;
+	virtual void getInt32(const std::string & attr_name, const PODArray<id_t> & ids, const PODArray<Int32> & def, PODArray<Int32> & out) const = 0;
+	virtual void getInt64(const std::string & attr_name, const PODArray<id_t> & ids, const PODArray<Int64> & def, PODArray<Int64> & out) const = 0;
+	virtual void getFloat32(const std::string & attr_name, const PODArray<id_t> & ids, const PODArray<Float32> & def, PODArray<Float32> & out) const = 0;
+	virtual void getFloat64(const std::string & attr_name, const PODArray<id_t> & ids, const PODArray<Float64> & def, PODArray<Float64> & out) const = 0;
+	virtual void getString(const std::string & attr_name, const PODArray<id_t> & ids, const ColumnString * def, ColumnString * out) const = 0;
+
+	virtual void has(const PODArray<id_t> & ids, PODArray<UInt8> & out) const = 0;
 };
 
 }

dbms/include/DB/Dictionaries/IDictionarySource.h

@@ -27,6 +27,11 @@ public:
 	/// returns an input stream with the data for a collection of identifiers
 	virtual BlockInputStreamPtr loadIds(const std::vector<std::uint64_t> & ids) = 0;
 
+	/** returns an input stream with the data for a collection of composite keys.
+	 *	`requested_rows` contains indices of all rows containing unique keys. */
+	virtual BlockInputStreamPtr loadKeys(
+		const ConstColumnPlainPtrs & key_columns, const std::vector<std::size_t> & requested_rows) = 0;
+
 	/// indicates whether the source has been modified since last load* operation
 	virtual bool isModified() const = 0;
 

dbms/include/DB/Dictionaries/MongoDBDictionarySource.h

@@ -4,6 +4,7 @@
 #include <DB/Dictionaries/MongoDBBlockInputStream.h>
 #include <Poco/Util/AbstractConfiguration.h>
 #include <mongo/client/dbclient.h>
+#include <ext/collection_cast.hpp>
 
 
 namespace DB
@@ -97,9 +98,12 @@ public:
 
 	BlockInputStreamPtr loadIds(const std::vector<std::uint64_t> & ids) override
 	{
+		if (dict_struct.key)
+			throw Exception{"Complex key not supported", ErrorCodes::UNSUPPORTED_METHOD};
+
 		/// mongo::BSONObj has shitty design and does not use fixed width integral types
-		const std::vector<long long int> iids{std::begin(ids), std::end(ids)};
-		const auto ids_enumeration = BSON(dict_struct.id.name << BSON("$in" << iids));
+		const auto ids_enumeration = BSON(
+			dict_struct.id->name << BSON("$in" << ext::collection_cast<std::vector<long long int>>(ids)));
 
 		return new MongoDBBlockInputStream{
 			connection.query(db + '.' + collection, ids_enumeration, 0, 0, &fields_to_query),
@@ -107,6 +111,12 @@ public:
 		};
 	}
 
+	BlockInputStreamPtr loadKeys(
+		const ConstColumnPlainPtrs & key_columns, const std::vector<std::size_t> & requested_rows) override
+	{
+		throw Exception{"Method unsupported", ErrorCodes::NOT_IMPLEMENTED};
+	}
+
 	/// @todo: for MongoDB, modification date can somehow be determined from the `_id` object field
 	bool isModified() const override { return false; }
 

dbms/include/DB/Dictionaries/MySQLDictionarySource.h

@@ -58,6 +58,15 @@ public:
 		return new MySQLBlockInputStream{pool.Get(), query, sample_block, max_block_size};
 	}
 
+	BlockInputStreamPtr loadKeys(
+		const ConstColumnPlainPtrs & key_columns, const std::vector<std::size_t> & requested_rows) override
+	{
+		/// Здесь не логгируем и не обновляем время модификации, так как запрос может быть большим, и часто задаваться.
+
+		const auto query = composeLoadKeysQuery(key_columns, requested_rows);
+		return new MySQLBlockInputStream{pool.Get(), query, sample_block, max_block_size};
+	}
+
 	bool isModified() const override
 	{
 		if (dont_check_update_time)
@@ -156,13 +165,15 @@ private:
 			WriteBufferFromString out{query};
 			writeString("SELECT ", out);
 
-			if (!dict_struct.id.expression.empty())
+			if (dict_struct.id)
 			{
-				writeParenthesisedString(dict_struct.id.expression, out);
+				if (!dict_struct.id->expression.empty())
+				{
+					writeParenthesisedString(dict_struct.id->expression, out);
 					writeString(" AS ", out);
 				}
 
-			writeProbablyBackQuotedString(dict_struct.id.name, out);
+				writeProbablyBackQuotedString(dict_struct.id->name, out);
 
 				if (dict_struct.range_min && dict_struct.range_max)
 				{
@@ -186,6 +197,26 @@ private:
 
 					writeProbablyBackQuotedString(dict_struct.range_max->name, out);
 				}
+			}
+			else if (dict_struct.key)
+			{
+				auto first = true;
+				for (const auto & key : *dict_struct.key)
+				{
+					if (!first)
+						writeString(", ", out);
+
+					first = false;
+
+					if (!key.expression.empty())
+					{
+						writeParenthesisedString(key.expression, out);
+						writeString(" AS ", out);
+					}
+
+					writeProbablyBackQuotedString(key.name, out);
+				}
+			}
 
 			for (const auto & attr : dict_struct.attributes)
 			{
@@ -222,19 +253,22 @@ private:
 
 	std::string composeLoadIdsQuery(const std::vector<std::uint64_t> & ids)
 	{
+		if (!dict_struct.id)
+			throw Exception{"Simple key required for method", ErrorCodes::UNSUPPORTED_METHOD};
+
 		std::string query;
 
 		{
 			WriteBufferFromString out{query};
 			writeString("SELECT ", out);
 
-			if (!dict_struct.id.expression.empty())
+			if (!dict_struct.id->expression.empty())
 			{
-				writeParenthesisedString(dict_struct.id.expression, out);
+				writeParenthesisedString(dict_struct.id->expression, out);
 				writeString(" AS ", out);
 			}
 
-			writeProbablyBackQuotedString(dict_struct.id.name, out);
+			writeProbablyBackQuotedString(dict_struct.id->name, out);
 
 			for (const auto & attr : dict_struct.attributes)
 			{
@@ -265,7 +299,7 @@ private:
 				writeString(" AND ", out);
 			}
 
-			writeProbablyBackQuotedString(dict_struct.id.name, out);
+			writeProbablyBackQuotedString(dict_struct.id->name, out);
 			writeString(" IN (", out);
 
 			auto first = true;
@@ -284,6 +318,92 @@ private:
 		return query;
 	}
 
+	std::string composeLoadKeysQuery(
+		const ConstColumnPlainPtrs & key_columns, const std::vector<std::size_t> & requested_rows)
+	{
+		if (!dict_struct.key)
+			throw Exception{"Composite key required for method", ErrorCodes::UNSUPPORTED_METHOD};
+
+		std::string query;
+
+		{
+			WriteBufferFromString out{query};
+			writeString("SELECT ", out);
+
+			auto first = true;
+			for (const auto & key_or_attribute : boost::join(*dict_struct.key, dict_struct.attributes))
+			{
+				if (!first)
+					writeString(", ", out);
+
+				first = false;
+
+				if (!key_or_attribute.expression.empty())
+				{
+					writeParenthesisedString(key_or_attribute.expression, out);
+					writeString(" AS ", out);
+				}
+
+				writeProbablyBackQuotedString(key_or_attribute.name, out);
+			}
+
+			writeString(" FROM ", out);
+			if (!db.empty())
+			{
+				writeProbablyBackQuotedString(db, out);
+				writeChar('.', out);
+			}
+			writeProbablyBackQuotedString(table, out);
+
+			writeString(" WHERE ", out);
+
+			if (!where.empty())
+			{
+				writeString(where, out);
+				writeString(" AND ", out);
+			}
+
+			first = true;
+			for (const auto row : requested_rows)
+			{
+				if (!first)
+					writeString(" OR ", out);
+
+				first = false;
+				composeKeyCondition(key_columns, row, out);
+			}
+
+			writeString(";", out);
+		}
+
+		return query;
+	}
+
+	void composeKeyCondition(const ConstColumnPlainPtrs & key_columns, const std::size_t row, WriteBuffer & out) const
+	{
+		writeString("(", out);
+
+		const auto keys_size = key_columns.size();
+		auto first = true;
+		for (const auto i : ext::range(0, keys_size))
+		{
+			if (!first)
+				writeString(" AND ", out);
+
+			first = false;
+
+			const auto & key_description = (*dict_struct.key)[i];
+			const auto & value = (*key_columns[i])[row];
+
+			/// key_i=value_i
+			writeString(key_description.name, out);
+			writeString("=", out);
+			key_description.type->serializeTextQuoted(value, out);
+		}
+
+		writeString(")", out);
+	}
+
 	const DictionaryStructure dict_struct;
 	const std::string db;
 	const std::string table;

dbms/include/DB/Dictionaries/RangeHashedDictionary.h

@@ -117,7 +117,7 @@ public:
 				const auto val_it = std::find_if(std::begin(ranges_and_values), std::end(ranges_and_values),
 					[date] (const value_t<StringRef> & v) { return v.range.contains(date); });
 
-				const auto string_ref = val_it != std::end(ranges_and_values) ? val_it->value : null_value;
+				const auto string_ref = val_it != std::end(ranges_and_values) ? val_it->value : StringRef{null_value};
 				out->insertData(string_ref.data, string_ref.size);
 			}
 			else

dbms/include/DB/Functions/FunctionsDictionaries.h

@@ -5,6 +5,7 @@
 #include <DB/DataTypes/DataTypeString.h>
 #include <DB/DataTypes/DataTypeDate.h>
 #include <DB/DataTypes/DataTypeDateTime.h>
+#include <DB/DataTypes/DataTypeTuple.h>
 
 #include <DB/Columns/ColumnVector.h>
 #include <DB/Columns/ColumnArray.h>
@@ -18,6 +19,8 @@
 #include <DB/Dictionaries/FlatDictionary.h>
 #include <DB/Dictionaries/HashedDictionary.h>
 #include <DB/Dictionaries/CacheDictionary.h>
+#include <DB/Dictionaries/ComplexKeyHashedDictionary.h>
+#include <DB/Dictionaries/ComplexKeyCacheDictionary.h>
 #include <DB/Dictionaries/RangeHashedDictionary.h>
 
 #include <ext/range.hpp>
@@ -739,6 +742,156 @@ public:
 };
 
 
+class FunctionDictHas final : public IFunction
+{
+public:
+	static constexpr auto name = "dictHas";
+
+	static IFunction * create(const Context & context)
+	{
+		return new FunctionDictHas{context.getExternalDictionaries()};
+	}
+
+	FunctionDictHas(const ExternalDictionaries & dictionaries) : dictionaries(dictionaries) {}
+
+	String getName() const override { return name; }
+
+private:
+	DataTypePtr getReturnType(const DataTypes & arguments) const override
+	{
+		if (arguments.size() != 2)
+			throw Exception{
+				"Number of arguments for function " + getName() + " doesn't match: passed "
+					+ toString(arguments.size()) + ", should be 2.",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		if (!typeid_cast<const DataTypeString *>(arguments[0].get()))
+			throw Exception{
+				"Illegal type " + arguments[0]->getName() + " of first argument of function " + getName()
+					+ ", expected a string.",
+				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
+			};
+
+		if (!typeid_cast<const DataTypeUInt64 *>(arguments[1].get()) &&
+			!typeid_cast<const DataTypeTuple *>(arguments[1].get()))
+			throw Exception{
+				"Illegal type " + arguments[1]->getName() + " of second argument of function " + getName()
+					+ ", must be UInt64 or tuple(...).",
+				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
+			};
+
+		return new DataTypeUInt8;
+	}
+
+	void execute(Block & block, const ColumnNumbers & arguments, const size_t result) override
+	{
+		const auto dict_name_col = typeid_cast<const ColumnConst<String> *>(block.getByPosition(arguments[0]).column.get());
+		if (!dict_name_col)
+			throw Exception{
+				"First argument of function " + getName() + " must be a constant string",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		auto dict = dictionaries.getDictionary(dict_name_col->getData());
+		const auto dict_ptr = dict.get();
+
+		if (!executeDispatchSimple<FlatDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchSimple<HashedDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchSimple<CacheDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchComplex<ComplexKeyHashedDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchComplex<ComplexKeyCacheDictionary>(block, arguments, result, dict_ptr))
+			throw Exception{
+				"Unsupported dictionary type " + dict_ptr->getTypeName(),
+				ErrorCodes::UNKNOWN_TYPE
+			};
+	}
+
+	template <typename DictionaryType>
+	bool executeDispatchSimple(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const IDictionaryBase * const dictionary)
+	{
+		const auto dict = typeid_cast<const DictionaryType *>(dictionary);
+		if (!dict)
+			return false;
+
+		if (arguments.size() != 2)
+			throw Exception{
+				"Function " + getName() + " for dictionary of type " + dict->getTypeName() +
+					" requires exactly 2 arguments",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		const auto id_col_untyped = block.getByPosition(arguments[1]).column.get();
+		if (const auto id_col = typeid_cast<const ColumnVector<UInt64> *>(id_col_untyped))
+		{
+			const auto & ids = id_col->getData();
+
+			const auto out = new ColumnVector<UInt8>(ext::size(ids));
+			block.getByPosition(result).column = out;
+
+			dict->has(ids, out->getData());
+		}
+		else if (const auto id_col = typeid_cast<const ColumnConst<UInt64> *>(id_col_untyped))
+		{
+			const PODArray<UInt64> ids(1, id_col->getData());
+			PODArray<UInt8> out(1);
+
+			dict->has(ids, out);
+
+			block.getByPosition(result).column = new ColumnConst<UInt8>{id_col->size(), out.front()};
+		}
+		else
+			throw Exception{
+				"Second argument of function " + getName() + " must be UInt64",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		return true;
+	}
+
+	template <typename DictionaryType>
+	bool executeDispatchComplex(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const IDictionaryBase * const dictionary)
+	{
+		const auto dict = typeid_cast<const DictionaryType *>(dictionary);
+		if (!dict)
+			return false;
+
+		if (arguments.size() != 2)
+			throw Exception{
+				"Function " + getName() + " for dictionary of type " + dict->getTypeName() +
+					" requires exactly 2 arguments",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		const auto key_col_with_type = block.getByPosition(arguments[1]);
+		if (const auto key_col = typeid_cast<const ColumnTuple *>(key_col_with_type.column.get()))
+		{
+			const auto key_columns = ext::map<ConstColumnPlainPtrs>(key_col->getColumns(), [] (const ColumnPtr & ptr) {
+				return ptr.get();
+			});
+
+			const auto & key_types = static_cast<const DataTypeTuple &>(*key_col_with_type.type).getElements();
+
+			const auto out = new ColumnVector<UInt8>(key_col->size());
+			block.getByPosition(result).column = out;
+
+			dict->has(key_columns, key_types, out->getData());
+		}
+		else
+			throw Exception{
+				"Second argument of function " + getName() + " must be " + dict->getKeyDescription(),
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		return true;
+	}
+
+	const ExternalDictionaries & dictionaries;
+};
+
+
 class FunctionDictGetString final : public IFunction
 {
 public:
@@ -781,11 +934,12 @@ private:
 			};
 		}
 
-		if (!typeid_cast<const DataTypeUInt64 *>(arguments[2].get()))
+		if (!typeid_cast<const DataTypeUInt64 *>(arguments[2].get()) &&
+			!typeid_cast<const DataTypeTuple *>(arguments[2].get()))
 		{
 			throw Exception{
 				"Illegal type " + arguments[2]->getName() + " of third argument of function " + getName()
-					+ ", must be UInt64.",
+					+ ", must be UInt64 or tuple(...).",
 				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
 			};
 		}
@@ -817,6 +971,8 @@ private:
 		if (!executeDispatch<FlatDictionary>(block, arguments, result, dict_ptr) &&
 			!executeDispatch<HashedDictionary>(block, arguments, result, dict_ptr) &&
 			!executeDispatch<CacheDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchComplex<ComplexKeyHashedDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchComplex<ComplexKeyCacheDictionary>(block, arguments, result, dict_ptr) &&
 			!executeDispatchRange<RangeHashedDictionary>(block, arguments, result, dict_ptr))
 			throw Exception{
 				"Unsupported dictionary type " + dict_ptr->getTypeName(),
@@ -876,6 +1032,53 @@ private:
 		return true;
 	}
 
+	template <typename DictionaryType>
+	bool executeDispatchComplex(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const IDictionaryBase * const dictionary)
+	{
+		const auto dict = typeid_cast<const DictionaryType *>(dictionary);
+		if (!dict)
+			return false;
+
+		if (arguments.size() != 3)
+			throw Exception{
+				"Function " + getName() + " for dictionary of type " + dict->getTypeName() +
+					" requires exactly 3 arguments",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		const auto attr_name_col = typeid_cast<const ColumnConst<String> *>(block.getByPosition(arguments[1]).column.get());
+		if (!attr_name_col)
+			throw Exception{
+				"Second argument of function " + getName() + " must be a constant string",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		const auto & attr_name = attr_name_col->getData();
+
+		const auto key_col_with_type = block.getByPosition(arguments[2]);
+		if (const auto key_col = typeid_cast<const ColumnTuple *>(key_col_with_type.column.get()))
+		{
+			const auto key_columns = ext::map<ConstColumnPlainPtrs>(key_col->getColumns(), [] (const ColumnPtr & ptr) {
+				return ptr.get();
+			});
+
+			const auto & key_types = static_cast<const DataTypeTuple &>(*key_col_with_type.type).getElements();
+
+			const auto out = new ColumnString;
+			block.getByPosition(result).column = out;
+
+			dict->getString(attr_name, key_columns, key_types, out);
+		}
+		else
+			throw Exception{
+				"Third argument of function " + getName() + " must be " + dict->getKeyDescription(),
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		return true;
+	}
+
 	template <typename DictionaryType>
 	bool executeDispatchRange(
 		Block & block, const ColumnNumbers & arguments, const size_t result, const IDictionaryBase * const dictionary)
@@ -983,6 +1186,256 @@ private:
 };
 
 
+class FunctionDictGetStringOrDefault final : public IFunction
+{
+public:
+	static constexpr auto name = "dictGetStringOrDefault";
+
+	static IFunction * create(const Context & context)
+	{
+		return new FunctionDictGetStringOrDefault{context.getExternalDictionaries()};
+	}
+
+	FunctionDictGetStringOrDefault(const ExternalDictionaries & dictionaries) : dictionaries(dictionaries) {}
+
+	String getName() const override { return name; }
+
+private:
+	DataTypePtr getReturnType(const DataTypes & arguments) const override
+	{
+		if (arguments.size() != 4)
+			throw Exception{
+				"Number of arguments for function " + getName() + " doesn't match: passed " +
+					toString(arguments.size()) + ", should be 4.",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		if (!typeid_cast<const DataTypeString *>(arguments[0].get()))
+			throw Exception{
+				"Illegal type " + arguments[0]->getName() + " of first argument of function " + getName() +
+					", expected a string.",
+				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
+			};
+
+		if (!typeid_cast<const DataTypeString *>(arguments[1].get()))
+			throw Exception{
+				"Illegal type " + arguments[1]->getName() + " of second argument of function " + getName() +
+					", expected a string.",
+				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
+			};
+
+		if (!typeid_cast<const DataTypeUInt64 *>(arguments[2].get()) &&
+			!typeid_cast<const DataTypeTuple *>(arguments[2].get()))
+		{
+			throw Exception{
+				"Illegal type " + arguments[2]->getName() + " of third argument of function " + getName()
+					+ ", must be UInt64 or tuple(...).",
+				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
+			};
+		}
+
+		if (!typeid_cast<const DataTypeString *>(arguments[3].get()))
+			throw Exception{
+				"Illegal type " + arguments[3]->getName() + " of fourth argument of function " + getName() +
+					", must be String.",
+				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
+			};
+
+		return new DataTypeString;
+	}
+
+	void execute(Block & block, const ColumnNumbers & arguments, const size_t result)
+	{
+		const auto dict_name_col = typeid_cast<const ColumnConst<String> *>(block.getByPosition(arguments[0]).column.get());
+		if (!dict_name_col)
+			throw Exception{
+				"First argument of function " + getName() + " must be a constant string",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		auto dict = dictionaries.getDictionary(dict_name_col->getData());
+		const auto dict_ptr = dict.get();
+
+		if (!executeDispatch<FlatDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatch<HashedDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatch<CacheDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchComplex<ComplexKeyHashedDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchComplex<ComplexKeyCacheDictionary>(block, arguments, result, dict_ptr))
+			throw Exception{
+				"Unsupported dictionary type " + dict_ptr->getTypeName(),
+				ErrorCodes::UNKNOWN_TYPE
+			};
+	}
+
+	template <typename DictionaryType>
+	bool executeDispatch(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const IDictionaryBase * const dictionary)
+	{
+		const auto dict = typeid_cast<const DictionaryType *>(dictionary);
+		if (!dict)
+			return false;
+
+		if (arguments.size() != 4)
+			throw Exception{
+				"Function " + getName() + " for dictionary of type " + dict->getTypeName() +
+					" requires exactly 4 arguments",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		const auto attr_name_col = typeid_cast<const ColumnConst<String> *>(block.getByPosition(arguments[1]).column.get());
+		if (!attr_name_col)
+			throw Exception{
+				"Second argument of function " + getName() + " must be a constant string",
+					ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		const auto & attr_name = attr_name_col->getData();
+
+		const auto id_col_untyped = block.getByPosition(arguments[2]).column.get();
+		if (const auto id_col = typeid_cast<const ColumnVector<UInt64> *>(id_col_untyped))
+			executeDispatch(block, arguments, result, dict, attr_name, id_col);
+		else if (const auto id_col = typeid_cast<const ColumnConst<UInt64> *>(id_col_untyped))
+			executeDispatch(block, arguments, result, dict, attr_name, id_col);
+		else
+			throw Exception{
+				"Third argument of function " + getName() + " must be UInt64",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		return true;
+	}
+
+	template <typename DictionaryType>
+	void executeDispatch(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const DictionaryType * const dictionary,
+		const std::string & attr_name, const ColumnVector<UInt64> * const id_col)
+	{
+		const auto default_col_untyped = block.getByPosition(arguments[3]).column.get();
+
+		if (const auto default_col = typeid_cast<const ColumnString *>(default_col_untyped))
+		{
+			/// vector ids, vector defaults
+			const auto out = new ColumnString;
+			block.getByPosition(result).column = out;
+			dictionary->getString(attr_name, id_col->getData(), default_col, out);
+		}
+		else if (const auto default_col =  typeid_cast<const ColumnConst<String> *>(default_col_untyped))
+		{
+			/// vector ids, const defaults
+			const auto out = new ColumnString;
+			block.getByPosition(result).column = out;
+
+			/// @todo avoid materialization
+			const auto default_col_materialized = default_col->convertToFullColumn();
+
+			dictionary->getString(attr_name, id_col->getData(),
+				static_cast<const ColumnString *>(default_col_materialized.get()), out);
+		}
+		else
+			throw Exception{
+				"Fourth argument of function " + getName() + " must be String",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+	}
+
+	template <typename DictionaryType>
+	void executeDispatch(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const DictionaryType * const dictionary,
+		const std::string & attr_name, const ColumnConst<UInt64> * const id_col)
+	{
+		const auto default_col_untyped = block.getByPosition(arguments[3]).column.get();
+
+		if (const auto default_col = typeid_cast<const ColumnString *>(default_col_untyped))
+		{
+			/// const ids, vector defaults
+			/// @todo avoid materialization
+			const PODArray<UInt64> ids(id_col->size(), id_col->getData());
+			const auto out = new ColumnString;
+			block.getByPosition(result).column = out;
+
+			dictionary->getString(attr_name, ids, default_col, out);
+		}
+		else if (const auto default_col = typeid_cast<const ColumnConst<String> *>(default_col_untyped))
+		{
+			/// const ids, const defaults
+			const PODArray<UInt64> ids(1, id_col->getData());
+			auto out = std::make_unique<ColumnString>();
+
+			/// create ColumnString with default
+			const auto defs = std::make_unique<ColumnString>();
+			defs->insert(Field{default_col->getData()});
+
+			dictionary->getString(attr_name, ids, defs.get(), out.get());
+
+			block.getByPosition(result).column = new ColumnConst<String>{
+				id_col->size(), out->getDataAt(0).toString()
+			};
+		}
+		else
+			throw Exception{
+				"Fourth argument of function " + getName() + " must be String",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+	}
+
+	template <typename DictionaryType>
+	bool executeDispatchComplex(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const IDictionaryBase * const dictionary)
+	{
+		const auto dict = typeid_cast<const DictionaryType *>(dictionary);
+		if (!dict)
+			return false;
+
+		if (arguments.size() != 4)
+			throw Exception{
+				"Function " + getName() + " for dictionary of type " + dict->getTypeName() +
+					" requires exactly 4 arguments",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		const auto attr_name_col = typeid_cast<const ColumnConst<String> *>(block.getByPosition(arguments[1]).column.get());
+		if (!attr_name_col)
+			throw Exception{
+				"Second argument of function " + getName() + " must be a constant string",
+					ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		const auto & attr_name = attr_name_col->getData();
+
+		const auto key_col_with_type = block.getByPosition(arguments[2]);
+		const auto & key_col = typeid_cast<const ColumnTuple &>(*key_col_with_type.column);
+		const auto key_columns = ext::map<ConstColumnPlainPtrs>(key_col.getColumns(), [] (const ColumnPtr & ptr) {
+			return ptr.get();
+		});
+		const auto & key_types = static_cast<const DataTypeTuple &>(*key_col_with_type.type).getElements();
+
+		const auto out = new ColumnString;
+		block.getByPosition(result).column = out;
+
+		const auto default_col_untyped = block.getByPosition(arguments[3]).column.get();
+		if (const auto default_col = typeid_cast<const ColumnString *>(default_col_untyped))
+			dict->getString(attr_name, key_columns, key_types, default_col, out);
+		else if (const auto default_col = typeid_cast<const ColumnConst<String> *>(default_col_untyped))
+		{
+			/// @todo avoid materialization
+			const auto default_col_materialized = default_col->convertToFullColumn();
+
+			dict->getString(attr_name, key_columns, key_types,
+				static_cast<const ColumnString *>(default_col_materialized.get()), out);
+		}
+		else
+			throw Exception{
+				"Fourth argument of function " + getName() + " must be String",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		return true;
+	}
+
+	const ExternalDictionaries & dictionaries;
+};
+
+
 template <typename DataType> struct DictGetTraits;
 #define DECLARE_DICT_GET_TRAITS(TYPE, DATA_TYPE) \
 template <> struct DictGetTraits<DATA_TYPE>\
@@ -995,12 +1448,33 @@ template <> struct DictGetTraits<DATA_TYPE>\
 		dict->get##TYPE(name, ids, out);\
 	}\
 	template <typename DictionaryType>\
+	static void get(\
+		const DictionaryType * const dict, const std::string & name, const ConstColumnPlainPtrs & key_columns,\
+		const DataTypes & key_types, PODArray<TYPE> & out)\
+	{\
+		dict->get##TYPE(name, key_columns, key_types, out);\
+	}\
+	template <typename DictionaryType>\
 	static void get(\
 		const DictionaryType * const dict, const std::string & name, const PODArray<UInt64> & ids,\
 		const PODArray<UInt16> & dates, PODArray<TYPE> & out)\
 	{\
 		dict->get##TYPE(name, ids, dates, out);\
 	}\
+	template <typename DictionaryType>\
+	static void getOrDefault(\
+		const DictionaryType * const dict, const std::string & name, const PODArray<UInt64> & ids,\
+		const PODArray<TYPE> & def, PODArray<TYPE> & out)\
+	{\
+		dict->get##TYPE(name, ids, def, out);\
+	}\
+	template <typename DictionaryType>\
+	static void getOrDefault(\
+		const DictionaryType * const dict, const std::string & name, const ConstColumnPlainPtrs & key_columns,\
+		const DataTypes & key_types, const PODArray<TYPE> & def, PODArray<TYPE> & out)\
+	{\
+		dict->get##TYPE(name, key_columns, key_types, def, out);\
+	}\
 };
 DECLARE_DICT_GET_TRAITS(UInt8, DataTypeUInt8)
 DECLARE_DICT_GET_TRAITS(UInt16, DataTypeUInt16)
@@ -1061,11 +1535,12 @@ private:
 			};
 		}
 
-		if (!typeid_cast<const DataTypeUInt64 *>(arguments[2].get()))
+		if (!typeid_cast<const DataTypeUInt64 *>(arguments[2].get()) &&
+			!typeid_cast<const DataTypeTuple *>(arguments[2].get()))
 		{
 			throw Exception{
 				"Illegal type " + arguments[2]->getName() + " of third argument of function " + getName()
-					+ ", must be UInt64.",
+					+ ", must be UInt64 or tuple(...).",
 				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
 			};
 		}
@@ -1097,6 +1572,8 @@ private:
 		if (!executeDispatch<FlatDictionary>(block, arguments, result, dict_ptr) &&
 			!executeDispatch<HashedDictionary>(block, arguments, result, dict_ptr) &&
 			!executeDispatch<CacheDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchComplex<ComplexKeyHashedDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchComplex<ComplexKeyCacheDictionary>(block, arguments, result, dict_ptr) &&
 			!executeDispatchRange<RangeHashedDictionary>(block, arguments, result, dict_ptr))
 			throw Exception{
 				"Unsupported dictionary type " + dict_ptr->getTypeName(),
@@ -1131,13 +1608,11 @@ private:
 		const auto id_col_untyped = block.getByPosition(arguments[2]).column.get();
 		if (const auto id_col = typeid_cast<const ColumnVector<UInt64> *>(id_col_untyped))
 		{
-			const auto out = new ColumnVector<Type>;
+			const auto out = new ColumnVector<Type>(id_col->size());
 			block.getByPosition(result).column = out;
 
 			const auto & ids = id_col->getData();
 			auto & data = out->getData();
-			const auto size = ids.size();
-			data.resize(size);
 
 			DictGetTraits<DataType>::get(dict, attr_name, ids, data);
 		}
@@ -1160,6 +1635,55 @@ private:
 		return true;
 	}
 
+	template <typename DictionaryType>
+	bool executeDispatchComplex(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const IDictionaryBase * const dictionary)
+	{
+		const auto dict = typeid_cast<const DictionaryType *>(dictionary);
+		if (!dict)
+			return false;
+
+		if (arguments.size() != 3)
+			throw Exception{
+				"Function " + getName() + " for dictionary of type " + dict->getTypeName() +
+					" requires exactly 3 arguments",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		const auto attr_name_col = typeid_cast<const ColumnConst<String> *>(block.getByPosition(arguments[1]).column.get());
+		if (!attr_name_col)
+			throw Exception{
+				"Second argument of function " + getName() + " must be a constant string",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		const auto & attr_name = attr_name_col->getData();
+
+		const auto key_col_with_type = block.getByPosition(arguments[2]);
+		if (const auto key_col = typeid_cast<const ColumnTuple *>(key_col_with_type.column.get()))
+		{
+			const auto key_columns = ext::map<ConstColumnPlainPtrs>(key_col->getColumns(), [] (const ColumnPtr & ptr) {
+				return ptr.get();
+			});
+
+			const auto & key_types = static_cast<const DataTypeTuple &>(*key_col_with_type.type).getElements();
+
+			const auto out = new ColumnVector<Type>(key_columns.front()->size());
+			block.getByPosition(result).column = out;
+
+			auto & data = out->getData();
+
+			DictGetTraits<DataType>::get(dict, attr_name, key_columns, key_types, data);
+		}
+		else
+			throw Exception{
+				"Third argument of function " + getName() + " must be " + dict->getKeyDescription(),
+				ErrorCodes::TYPE_MISMATCH
+			};
+
+		return true;
+	}
+
 	template <typename DictionaryType>
 	bool executeDispatchRange(
 		Block & block, const ColumnNumbers & arguments, const size_t result, const IDictionaryBase * const dictionary)
@@ -1295,6 +1819,294 @@ using FunctionDictGetDate = FunctionDictGet<DataTypeDate>;
 using FunctionDictGetDateTime = FunctionDictGet<DataTypeDateTime>;
 
 
+template <typename DataType>
+class FunctionDictGetOrDefault final : public IFunction
+{
+	using Type = typename DataType::FieldType;
+
+public:
+	static const std::string name;
+
+	static IFunction * create(const Context & context)
+	{
+		return new FunctionDictGetOrDefault{context.getExternalDictionaries()};
+	}
+
+	FunctionDictGetOrDefault(const ExternalDictionaries & dictionaries) : dictionaries(dictionaries) {}
+
+	String getName() const override { return name; }
+
+private:
+	DataTypePtr getReturnType(const DataTypes & arguments) const override
+	{
+		if (arguments.size() != 4)
+			throw Exception{
+				"Number of arguments for function " + getName() + " doesn't match: passed "
+					+ toString(arguments.size()) + ", should be 4.",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		if (!typeid_cast<const DataTypeString *>(arguments[0].get()))
+		{
+			throw Exception{
+				"Illegal type " + arguments[0]->getName() + " of first argument of function " + getName()
+					+ ", expected a string.",
+				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
+			};
+		}
+
+		if (!typeid_cast<const DataTypeString *>(arguments[1].get()))
+		{
+			throw Exception{
+				"Illegal type " + arguments[1]->getName() + " of second argument of function " + getName()
+					+ ", expected a string.",
+				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
+			};
+		}
+
+		if (!typeid_cast<const DataTypeUInt64 *>(arguments[2].get()) &&
+			!typeid_cast<const DataTypeTuple *>(arguments[2].get()))
+		{
+			throw Exception{
+				"Illegal type " + arguments[2]->getName() + " of third argument of function " + getName()
+					+ ", must be UInt64 or tuple(...).",
+				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
+			};
+		}
+
+		if (!typeid_cast<const DataType *>(arguments[3].get()))
+		{
+			throw Exception{
+				"Illegal type " + arguments[3]->getName() + " of fourth argument of function " + getName()
+					+ ", must be " + DataType{}.getName() + ".",
+				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT
+			};
+		}
+
+		return new DataType;
+	}
+
+	void execute(Block & block, const ColumnNumbers & arguments, const size_t result) override
+	{
+		const auto dict_name_col = typeid_cast<const ColumnConst<String> *>(block.getByPosition(arguments[0]).column.get());
+		if (!dict_name_col)
+			throw Exception{
+				"First argument of function " + getName() + " must be a constant string",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		auto dict = dictionaries.getDictionary(dict_name_col->getData());
+		const auto dict_ptr = dict.get();
+
+		if (!executeDispatch<FlatDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatch<HashedDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatch<CacheDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchComplex<ComplexKeyHashedDictionary>(block, arguments, result, dict_ptr) &&
+			!executeDispatchComplex<ComplexKeyCacheDictionary>(block, arguments, result, dict_ptr))
+			throw Exception{
+				"Unsupported dictionary type " + dict_ptr->getTypeName(),
+				ErrorCodes::UNKNOWN_TYPE
+			};
+	}
+
+	template <typename DictionaryType>
+	bool executeDispatch(Block & block, const ColumnNumbers & arguments, const size_t result,
+		const IDictionaryBase * const dictionary)
+	{
+		const auto dict = typeid_cast<const DictionaryType *>(dictionary);
+		if (!dict)
+			return false;
+
+		if (arguments.size() != 4)
+			throw Exception{
+				"Function " + getName() + " for dictionary of type " + dict->getTypeName() +
+				" requires exactly 4 arguments.",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		const auto attr_name_col = typeid_cast<const ColumnConst<String> *>(block.getByPosition(arguments[1]).column.get());
+		if (!attr_name_col)
+			throw Exception{
+				"Second argument of function " + getName() + " must be a constant string",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		const auto & attr_name = attr_name_col->getData();
+
+		const auto id_col_untyped = block.getByPosition(arguments[2]).column.get();
+		if (const auto id_col = typeid_cast<const ColumnVector<UInt64> *>(id_col_untyped))
+			executeDispatch(block, arguments, result, dict, attr_name, id_col);
+		else if (const auto id_col = typeid_cast<const ColumnConst<UInt64> *>(id_col_untyped))
+			executeDispatch(block, arguments, result, dict, attr_name, id_col);
+		else
+			throw Exception{
+				"Third argument of function " + getName() + " must be UInt64",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		return true;
+	}
+
+	template <typename DictionaryType>
+	void executeDispatch(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const DictionaryType * const dictionary,
+		const std::string & attr_name, const ColumnVector<UInt64> * const id_col)
+	{
+		const auto default_col_untyped = block.getByPosition(arguments[3]).column.get();
+
+		if (const auto default_col = typeid_cast<const ColumnVector<Type> *>(default_col_untyped))
+		{
+			/// vector ids, vector defaults
+			const auto out = new ColumnVector<Type>(id_col->size());
+			block.getByPosition(result).column = out;
+
+			const auto & ids = id_col->getData();
+			auto & data = out->getData();
+			const auto & defs = default_col->getData();
+
+			DictGetTraits<DataType>::getOrDefault(dictionary, attr_name, ids, defs, data);
+		}
+		else if (const auto default_col =  typeid_cast<const ColumnConst<Type> *>(default_col_untyped))
+		{
+			/// vector ids, const defaults
+			const auto out = new ColumnVector<Type>(id_col->size());
+			block.getByPosition(result).column = out;
+
+			const auto & ids = id_col->getData();
+			auto & data = out->getData();
+
+			/// @todo avoid materialization
+			const PODArray<Type> defs(id_col->size(), default_col->getData());
+
+			DictGetTraits<DataType>::getOrDefault(dictionary, attr_name, ids, defs, data);
+		}
+		else
+			throw Exception{
+				"Fourth argument of function " + getName() + " must be " + DataType{}.getName(),
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+	}
+
+	template <typename DictionaryType>
+	void executeDispatch(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const DictionaryType * const dictionary,
+		const std::string & attr_name, const ColumnConst<UInt64> * const id_col)
+	{
+		const auto default_col_untyped = block.getByPosition(arguments[3]).column.get();
+
+		if (const auto default_col = typeid_cast<const ColumnVector<Type> *>(default_col_untyped))
+		{
+			/// const ids, vector defaults
+			/// @todo avoid materialization
+			const PODArray<UInt64> ids(id_col->size(), id_col->getData());
+
+			const auto out = new ColumnVector<Type>(id_col->size());
+			block.getByPosition(result).column = out;
+
+			auto & data = out->getData();
+			const auto & defs = default_col->getData();
+
+			DictGetTraits<DataType>::getOrDefault(dictionary, attr_name, ids, defs, data);
+		}
+		else if (const auto default_col = typeid_cast<const ColumnConst<Type> *>(default_col_untyped))
+		{
+			/// const ids, const defaults
+			const PODArray<UInt64> ids(1, id_col->getData());
+			PODArray<Type> data(1);
+			const PODArray<Type> defs(1, default_col->getData());
+			DictGetTraits<DataType>::getOrDefault(dictionary, attr_name, ids, defs, data);
+
+			block.getByPosition(result).column = new ColumnConst<Type>{id_col->size(), data.front()};
+		}
+		else
+			throw Exception{
+				"Fourth argument of function " + getName() + " must be " + DataType{}.getName(),
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+	}
+
+	template <typename DictionaryType>
+	bool executeDispatchComplex(
+		Block & block, const ColumnNumbers & arguments, const size_t result, const IDictionaryBase * const dictionary)
+	{
+		const auto dict = typeid_cast<const DictionaryType *>(dictionary);
+		if (!dict)
+			return false;
+
+		if (arguments.size() != 4)
+			throw Exception{
+				"Function " + getName() + " for dictionary of type " + dict->getTypeName() +
+					" requires exactly 4 arguments",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH
+			};
+
+		const auto attr_name_col = typeid_cast<const ColumnConst<String> *>(block.getByPosition(arguments[1]).column.get());
+		if (!attr_name_col)
+			throw Exception{
+				"Second argument of function " + getName() + " must be a constant string",
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		const auto & attr_name = attr_name_col->getData();
+
+		const auto key_col_with_type = block.getByPosition(arguments[2]);
+		const auto & key_col = typeid_cast<const ColumnTuple &>(*key_col_with_type.column);
+		const auto key_columns = ext::map<ConstColumnPlainPtrs>(key_col.getColumns(), [] (const ColumnPtr & ptr) {
+			return ptr.get();
+		});
+		const auto & key_types = static_cast<const DataTypeTuple &>(*key_col_with_type.type).getElements();
+
+		/// @todo detect when all key columns are constant
+		const auto rows = key_col.size();
+		const auto out = new ColumnVector<Type>(rows);
+		block.getByPosition(result).column = out;
+		auto & data = out->getData();
+
+		const auto default_col_untyped = block.getByPosition(arguments[3]).column.get();
+		if (const auto default_col = typeid_cast<const ColumnVector<Type> *>(default_col_untyped))
+		{
+			/// const defaults
+			const auto & defs = default_col->getData();
+
+			DictGetTraits<DataType>::getOrDefault(dict, attr_name, key_columns, key_types, defs, data);
+		}
+		else if (const auto default_col = typeid_cast<const ColumnConst<Type> *>(default_col_untyped))
+		{
+			/// @todo avoid materialization
+			const PODArray<Type> defs(rows, default_col->getData());
+
+			DictGetTraits<DataType>::getOrDefault(dict, attr_name, key_columns, key_types, defs, data);
+		}
+		else
+			throw Exception{
+				"Fourth argument of function " + getName() + " must be " + DataType{}.getName(),
+				ErrorCodes::ILLEGAL_COLUMN
+			};
+
+		return true;
+	}
+
+	const ExternalDictionaries & dictionaries;
+};
+
+template <typename DataType>
+const std::string FunctionDictGetOrDefault<DataType>::name = "dictGet" + DataType{}.getName() + "OrDefault";
+
+
+using FunctionDictGetUInt8OrDefault = FunctionDictGetOrDefault<DataTypeUInt8>;
+using FunctionDictGetUInt16OrDefault = FunctionDictGetOrDefault<DataTypeUInt16>;
+using FunctionDictGetUInt32OrDefault = FunctionDictGetOrDefault<DataTypeUInt32>;
+using FunctionDictGetUInt64OrDefault = FunctionDictGetOrDefault<DataTypeUInt64>;
+using FunctionDictGetInt8OrDefault = FunctionDictGetOrDefault<DataTypeInt8>;
+using FunctionDictGetInt16OrDefault = FunctionDictGetOrDefault<DataTypeInt16>;
+using FunctionDictGetInt32OrDefault = FunctionDictGetOrDefault<DataTypeInt32>;
+using FunctionDictGetInt64OrDefault = FunctionDictGetOrDefault<DataTypeInt64>;
+using FunctionDictGetFloat32OrDefault = FunctionDictGetOrDefault<DataTypeFloat32>;
+using FunctionDictGetFloat64OrDefault = FunctionDictGetOrDefault<DataTypeFloat64>;
+using FunctionDictGetDateOrDefault = FunctionDictGetOrDefault<DataTypeDate>;
+using FunctionDictGetDateTimeOrDefault = FunctionDictGetOrDefault<DataTypeDateTime>;
+
+
 class FunctionDictGetHierarchy final : public IFunction
 {
 public:

dbms/include/DB/Functions/FunctionsHashing.h

@@ -19,13 +19,12 @@
 #include <DB/Columns/ColumnConst.h>
 #include <DB/Columns/ColumnFixedString.h>
 #include <DB/Columns/ColumnArray.h>
+#include <DB/Columns/ColumnTuple.h>
 #include <DB/Common/HashTable/Hash.h>
 #include <DB/Functions/IFunction.h>
 
 #include <ext/range.hpp>
 
-#include <stats/IntHash.h>
-
 
 namespace DB
 {
@@ -399,6 +398,9 @@ UInt64 toInteger<Float64>(Float64 x)
 }
 
 
+/** Используются хэш-функции под названием CityHash, FarmHash, MetroHash.
+  * В связи с этим, этот шаблон назван со словами NeighbourhoodHash.
+  */
 template <typename Impl>
 class FunctionNeighbourhoodHash64 : public IFunction
 {
@@ -565,6 +567,29 @@ private:
 				ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
 	}
 
+	void executeForArgument(const IDataType * type, const IColumn * column, ColumnUInt64::Container_t & vec_to, bool & is_first)
+	{
+		/// Раскрытие кортежей.
+		if (const ColumnTuple * tuple = typeid_cast<const ColumnTuple *>(column))
+		{
+			const Block & tuple_data = tuple->getData();
+			for (size_t i = 0, size = tuple_data.columns(); i < size; ++i)
+			{
+				const ColumnWithTypeAndName & col = tuple_data.unsafeGetByPosition(i);
+				executeForArgument(col.type.get(), col.column.get(), vec_to, is_first);
+			}
+		}
+		else
+		{
+			if (is_first)
+				executeAny<true>(type, column, vec_to);
+			else
+				executeAny<false>(type, column, vec_to);
+		}
+
+		is_first = false;
+	}
+
 public:
 	/// Получить имя функции.
 	String getName() const override
@@ -589,20 +614,17 @@ public:
 
 		if (arguments.empty())
 		{
-			/// Случайное число из /dev/urandom используется как хеш пустого кортежа.
+			/// Случайное число из /dev/urandom используется как хеш пустого количества аргументов.
 			vec_to.assign(rows, 0xe28dbde7fe22e41c);
 		}
 
+		/// Функция поддерживает произвольное количество аргументов всевозможных типов.
+
+		bool is_first_argument = true;
 		for (size_t i = 0; i < arguments.size(); ++i)
 		{
-			const ColumnWithTypeAndName & column = block.getByPosition(arguments[i]);
-			const IDataType * from_type = &*column.type;
-			const IColumn * icolumn = &*column.column;
-
-			if (i == 0)
-				executeAny<true>(from_type, icolumn, vec_to);
-			else
-				executeAny<false>(from_type, icolumn, vec_to);
+			const ColumnWithTypeAndName & col = block.getByPosition(arguments[i]);
+			executeForArgument(col.type.get(), col.column.get(), vec_to, is_first_argument);
 		}
 	}
 };

dbms/include/DB/Functions/FunctionsMiscellaneous.h

@@ -339,11 +339,11 @@ public:
 	/// Выполнить функцию над блоком.
 	void execute(Block & block, const ColumnNumbers & arguments, size_t result) override
 	{
-		const IColumn & argument = *block.getByPosition(arguments[0]).column;
-		if (!argument.isConst())
-			throw Exception("Argument for function " + getName() + " must be constant.", ErrorCodes::ILLEGAL_COLUMN);
-
-		block.getByPosition(result).column = dynamic_cast<const IColumnConst &>(argument).convertToFullColumn();
+		const auto & src = block.getByPosition(arguments[0]).column;
+		if (auto converted = src->convertToFullColumnIfConst())
+			block.getByPosition(result).column = converted;
+		else
+			block.getByPosition(result).column = src;
 	}
 };
 
@@ -865,7 +865,7 @@ public:
 	}
 
 	template <typename T>
-	bool execute(Block & block, const IColumn * in_untyped, const size_t result) override
+	bool execute(Block & block, const IColumn * in_untyped, const size_t result)
 	{
 		if (const auto in = typeid_cast<const ColumnVector<T> *>(in_untyped))
 		{

dbms/include/DB/Functions/FunctionsRandom.h

@@ -5,7 +5,6 @@
 #include <DB/DataTypes/DataTypesNumberFixed.h>
 #include <DB/Functions/IFunction.h>
 #include <DB/Common/HashTable/Hash.h>
-#include <stats/IntHash.h>
 
 
 namespace DB

dbms/include/DB/IO/BufferWithOwnMemory.h

@@ -18,7 +18,7 @@ namespace DB
   * Отличается тем, что не делает лишний memset. (И почти ничего не делает.)
   * Также можно попросить выделять выровненный кусок памяти.
   */
-struct Memory : boost::noncopyable, Allocator
+struct Memory : boost::noncopyable, Allocator<false>
 {
 	size_t m_capacity = 0;
 	size_t m_size = 0;

dbms/include/DB/IO/DoubleConverter.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <src/double-conversion.h>
+#include <double-conversion/double-conversion.h>
 
 namespace DB
 {

dbms/include/DB/IO/ReadBufferAIO.h

@@ -55,11 +55,8 @@ private:
 	BufferWithOwnMemory<ReadBuffer> fill_buffer;
 
 	/// Описание асинхронного запроса на чтение.
-	iocb request = { 0 };
-	std::vector<iocb *> request_ptrs{&request};
-	std::vector<io_event> events{1};
-
-	AIOContext aio_context{1};
+	iocb request{};
+	std::future<ssize_t> future_bytes_read;
 
 	const std::string filename;
 

dbms/include/DB/Interpreters/Aggregator.h

@@ -743,6 +743,18 @@ struct AggregatedDataVariants : private boost::noncopyable
 typedef SharedPtr<AggregatedDataVariants> AggregatedDataVariantsPtr;
 typedef std::vector<AggregatedDataVariantsPtr> ManyAggregatedDataVariants;
 
+/** Как считаются "тотальные" значения при наличии WITH TOTALS?
+  * (Более подробно смотрите в TotalsHavingBlockInputStream.)
+  *
+  * В случае отсутствия group_by_overflow_mode = 'any', данные агрегируются как обычно, но состояния агрегатных функций не финализируются.
+  * Позже, состояния агрегатных функций для всех строк (прошедших через HAVING) мерджатся в одну - это и будет TOTALS.
+  *
+  * В случае наличия group_by_overflow_mode = 'any', данные агрегируются как обычно, кроме ключей, не поместившихся в max_rows_to_group_by.
+  * Для этих ключей, данные агрегируются в одну дополнительную строку - далее см. под названиями overflow_row, overflows...
+  * Позже, состояния агрегатных функций для всех строк (прошедших через HAVING) мерджатся в одну,
+  *  а также к ним прибавляется или не прибавляется (в зависимости от настройки totals_mode) также overflow_row - это и будет TOTALS.
+  */
+
 
 /** Агрегирует источник блоков.
   */
@@ -1032,7 +1044,7 @@ protected:
 		size_t rows,
 		Filler && filler) const;
 
-	BlocksList prepareBlocksAndFillWithoutKey(AggregatedDataVariants & data_variants, bool final) const;
+	BlocksList prepareBlocksAndFillWithoutKey(AggregatedDataVariants & data_variants, bool final, bool is_overflows) const;
 	BlocksList prepareBlocksAndFillSingleLevel(AggregatedDataVariants & data_variants, bool final) const;
 	BlocksList prepareBlocksAndFillTwoLevel(AggregatedDataVariants & data_variants, bool final, boost::threadpool::pool * thread_pool) const;
 

dbms/include/DB/Interpreters/ExpressionActions.h

@@ -69,7 +69,7 @@ public:
 	bool array_join_is_left;
 
 	/// Для JOIN
-	const Join * join = nullptr;
+	std::shared_ptr<const Join> join;
 	NamesAndTypesList columns_added_by_join;
 
 	/// Для PROJECT.
@@ -134,7 +134,7 @@ public:
 		return a;
 	}
 
-	static ExpressionAction ordinaryJoin(const Join * join_, const NamesAndTypesList & columns_added_by_join_)
+	static ExpressionAction ordinaryJoin(std::shared_ptr<const Join> join_, const NamesAndTypesList & columns_added_by_join_)
 	{
 		ExpressionAction a;
 		a.type = JOIN;

dbms/include/DB/Interpreters/ExpressionAnalyzer.h

@@ -208,6 +208,9 @@ private:
 	  */
 	void collectJoinedColumns(NameSet & joined_columns, NamesAndTypesList & joined_columns_name_type);
 
+	/** Добавляет ALIAS столбцы из storage в aliases, если запрос не является SELECT с ARRAY JOIN. При наличии
+	  * ARRAY JOIN их добавлять нельзя, иначе ломается логика его выполнения.
+	  */
 	void addStorageAliases();
 
 	/** Создать словарь алиасов.
@@ -229,6 +232,9 @@ private:
 	/// Превратить перечисление значений или подзапрос в ASTSet. node - функция in или notIn.
 	void makeSet(ASTFunction * node, const Block & sample_block);
 
+	/// Добавляет список ALIAS столбцов из таблицы
+	void addAliasColumns();
+
 	/// Замена скалярных подзапросов на значения-константы.
 	void executeScalarSubqueries();
 	void executeScalarSubqueriesImpl(ASTPtr & ast);

dbms/include/DB/Interpreters/InJoinSubqueriesPreprocessor.h

@@ -61,6 +61,21 @@ std::string getNameFromInSubqueryAttributes(IAST::Attributes attributes)
 	return name;
 }
 
+/// Проверить, указана ли таблица в секции FROM.
+bool isQueryFromTable(const ASTSelectQuery & query)
+{
+	if (query.table)
+	{
+		if (typeid_cast<const ASTSelectQuery *>(query.table.get()) != nullptr)
+			return false;
+		else if (typeid_cast<const ASTFunction *>(query.table.get()) != nullptr)
+			return false;
+		else
+			return true;
+	}
+	return false;
+}
+
 /// Проверить, является ли движок распределённым с количеством шардов более одного.
 template <typename TStorageDistributed>
 bool isEligibleStorageForInJoinPreprocessing(const StoragePtr & storage)
@@ -175,6 +190,7 @@ public:
 			else if ((node != static_cast<IAST *>(select_query))
 				&& ((sub_select_query = typeid_cast<ASTSelectQuery *>(node)) != nullptr))
 			{
+				if (isQueryFromTable(*sub_select_query))
 					++node->select_query_depth;
 				if (sub_select_query->enclosing_in_or_join != nullptr)
 				{

dbms/include/DB/Interpreters/InterpreterAlterQuery.h

@@ -4,7 +4,6 @@
 #include <DB/Storages/AlterCommands.h>
 #include <DB/Interpreters/Context.h>
 #include <DB/Interpreters/IInterpreter.h>
-#include <DB/Parsers/ASTIdentifier.h>
 
 namespace DB
 {

dbms/include/DB/Interpreters/InterpreterCheckQuery.h

@@ -2,7 +2,6 @@
 
 #include <DB/Interpreters/Context.h>
 #include <DB/Interpreters/IInterpreter.h>
-#include <DB/Parsers/ASTIdentifier.h>
 
 namespace DB
 {

dbms/include/DB/Interpreters/InterpreterDescribeQuery.h

@@ -2,7 +2,6 @@
 
 #include <DB/Storages/IStorage.h>
 #include <DB/Parsers/TablePropertiesQueriesASTs.h>
-#include <DB/Parsers/ASTIdentifier.h>
 #include <DB/Interpreters/Context.h>
 #include <DB/Interpreters/IInterpreter.h>
 #include <DB/DataStreams/OneBlockInputStream.h>

dbms/include/DB/Interpreters/InterpreterExistsQuery.h

@@ -2,7 +2,6 @@
 
 #include <DB/Storages/IStorage.h>
 #include <DB/Parsers/TablePropertiesQueriesASTs.h>
-#include <DB/Parsers/ASTIdentifier.h>
 #include <DB/Interpreters/Context.h>
 #include <DB/Interpreters/IInterpreter.h>
 #include <DB/DataStreams/OneBlockInputStream.h>

dbms/include/DB/Interpreters/InterpreterShowCreateQuery.h

@@ -2,7 +2,6 @@
 
 #include <DB/Storages/IStorage.h>
 #include <DB/Parsers/TablePropertiesQueriesASTs.h>
-#include <DB/Parsers/ASTIdentifier.h>
 #include <DB/Parsers/formatAST.h>
 #include <DB/Interpreters/Context.h>
 #include <DB/Interpreters/IInterpreter.h>

dbms/include/DB/Interpreters/Join.h

@@ -260,7 +260,7 @@ private:
 	void checkTypesOfKeys(const Block & block_left, const Block & block_right) const;
 };
 
-typedef Poco::SharedPtr<Join> JoinPtr;
+typedef std::shared_ptr<Join> JoinPtr;
 typedef std::vector<JoinPtr> Joins;
 
 

dbms/include/DB/Interpreters/Set.h

@@ -366,7 +366,8 @@ private:
 		size_t rows) const;
 };
 
-typedef Poco::SharedPtr<Set> SetPtr;
+typedef std::shared_ptr<Set> SetPtr;
+typedef std::shared_ptr<const Set> ConstSetPtr;
 typedef std::vector<SetPtr> Sets;
 
 

dbms/include/DB/Interpreters/Settings.h

@@ -16,6 +16,10 @@ namespace DB
   */
 struct Settings
 {
+	/// Для того, чтобы инициализация из пустого initializer-list была value initialization, а не aggregate initialization в С++14.
+	/// http://en.cppreference.com/w/cpp/language/aggregate_initialization
+	Settings() {}
+
 	/** Перечисление настроек: тип, имя, значение по-умолчанию.
 	  *
 	  * Это сделано несколько неудобно, чтобы не перечислять настройки во многих разных местах.
@@ -168,6 +172,8 @@ struct Settings
 	M(SettingUInt64, select_sequential_consistency, 0) \
 	/** Максимальное количество различных шардов и максимальное количество реплик одного шарда в функции remote. */ \
 	M(SettingUInt64, table_function_remote_max_addresses, 1000) \
+	/** Маскимальное количество потоков при распределённой обработке одного запроса **/ \
+	M(SettingUInt64, max_distributed_processing_threads, 8) \
 
 	/// Всевозможные ограничения на выполнение запроса.
 	Limits limits;

dbms/include/DB/Interpreters/evaluateMissingDefaults.h

@@ -44,8 +44,8 @@ inline void evaluateMissingDefaults(Block & block,
 	/// move evaluated columns to the original block, materializing them at the same time
 	for (auto & column_name_type : copy_block.getColumns())
 	{
-		if (column_name_type.column->isConst())
-			column_name_type.column = static_cast<const IColumnConst &>(*column_name_type.column).convertToFullColumn();
+		if (auto converted = column_name_type.column->convertToFullColumnIfConst())
+			column_name_type.column = converted;
 
 		block.insert(std::move(column_name_type));
 	}

dbms/include/DB/Interpreters/executeQuery.h

@@ -15,8 +15,8 @@ void executeQuery(
 	WriteBuffer & ostr,					/// Куда писать результат
 	Context & context,					/// БД, таблицы, типы данных, движки таблиц, функции, агрегатные функции...
 	BlockInputStreamPtr & query_plan,	/// Сюда может быть записано описание, как выполнялся запрос
-	bool internal = false,				/// Если true - значит запрос порождён из другого запроса, и не нужно его регистировать в ProcessList-е.
-	QueryProcessingStage::Enum stage = QueryProcessingStage::Complete);	/// До какой стадии выполнять SELECT запрос.
+	std::function<void(const String &)> set_content_type /// Может быть передан колбэк, с помощью которого может быть сообщён Content-Type формата.
+	);
 
 
 /** Более низкоуровневая функция для межсерверного взаимодействия.
@@ -35,8 +35,9 @@ void executeQuery(
   */
 BlockIO executeQuery(
 	const String & query,	/// Текст запроса, без данных INSERT-а (если есть). Данные INSERT-а следует писать в BlockIO::out.
-	Context & context,
-	bool internal = false,
-	QueryProcessingStage::Enum stage = QueryProcessingStage::Complete);
+	Context & context,		/// БД, таблицы, типы данных, движки таблиц, функции, агрегатные функции...
+	bool internal = false,	/// Если true - значит запрос порождён из другого запроса, и не нужно его регистировать в ProcessList-е.
+	QueryProcessingStage::Enum stage = QueryProcessingStage::Complete	/// До какой стадии выполнять SELECT запрос.
+	);
 
 }

dbms/include/DB/Parsers/ASTIdentifier.h

@@ -8,7 +8,7 @@
 namespace DB
 {
 
-/** Идентификатор (столбца или алиас, или именованый элемент кортежа)
+/** Идентификатор (столбца или алиас)
   */
 class ASTIdentifier : public ASTWithAlias
 {
@@ -21,7 +21,7 @@ public:
 		Format,
 	};
 
-	/// имя
+	/// имя. У составного идентификатора здесь будет конкатенированное имя (вида a.b.c), а отдельные составляюшие будут доступны внутри children.
 	String name;
 
 	/// чего идентифицирует этот идентификатор
@@ -44,16 +44,7 @@ public:
 	}
 
 protected:
-	void formatImplWithoutAlias(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const override
-	{
-		settings.ostr << (settings.hilite ? hilite_identifier : "");
-
-		WriteBufferFromOStream wb(settings.ostr, 32);
-		writeProbablyBackQuotedString(name, wb);
-		wb.next();
-
-		settings.ostr << (settings.hilite ? hilite_none : "");
-	}
+	void formatImplWithoutAlias(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const override;
 };
 
 }