Merge pull request #55061 from amosbird/support-empty-tuple-2

Support empty tuple [second implementation]

src/Columns/ColumnArray.cpp

@@ -828,7 +828,7 @@ ColumnPtr ColumnArray::filterTuple(const Filter & filt, ssize_t result_size_hint
     size_t tuple_size = tuple.tupleSize();
 
     if (tuple_size == 0)
-        throw Exception(ErrorCodes::LOGICAL_ERROR, "Empty tuple");
+        return filterGeneric(filt, result_size_hint);
 
     Columns temporary_arrays(tuple_size);
     for (size_t i = 0; i < tuple_size; ++i)
@@ -1265,7 +1265,7 @@ ColumnPtr ColumnArray::replicateTuple(const Offsets & replicate_offsets) const
     size_t tuple_size = tuple.tupleSize();
 
     if (tuple_size == 0)
-        throw Exception(ErrorCodes::LOGICAL_ERROR, "Empty tuple");
+        return replicateGeneric(replicate_offsets);
 
     Columns temporary_arrays(tuple_size);
     for (size_t i = 0; i < tuple_size; ++i)

src/Columns/ColumnSparse.cpp

@@ -820,6 +820,9 @@ ColumnPtr recursiveRemoveSparse(const ColumnPtr & column)
     if (const auto * column_tuple = typeid_cast<const ColumnTuple *>(column.get()))
     {
         auto columns = column_tuple->getColumns();
+        if (columns.empty())
+            return column;
+
         for (auto & element : columns)
             element = recursiveRemoveSparse(element);
 

src/Columns/ColumnTuple.cpp

@@ -3,14 +3,16 @@
 #include <Columns/ColumnCompressed.h>
 #include <Columns/IColumnImpl.h>
 #include <Core/Field.h>
+#include <Processors/Transforms/ColumnGathererTransform.h>
+#include <IO/Operators.h>
+#include <IO/WriteBufferFromString.h>
+#include <Common/Arena.h>
 #include <Common/WeakHash.h>
 #include <Common/assert_cast.h>
 #include <Common/iota.h>
 #include <Common/typeid_cast.h>
+#include <Columns/ColumnsCommon.h>
 #include <DataTypes/Serializations/SerializationInfoTuple.h>
-#include <IO/Operators.h>
-#include <IO/WriteBufferFromString.h>
-#include <Processors/Transforms/ColumnGathererTransform.h>
 #include <base/sort.h>
 
 
@@ -23,6 +25,7 @@ namespace ErrorCodes
     extern const int NOT_IMPLEMENTED;
     extern const int CANNOT_INSERT_VALUE_OF_DIFFERENT_SIZE_INTO_TUPLE;
     extern const int LOGICAL_ERROR;
+    extern const int SIZES_OF_COLUMNS_DOESNT_MATCH;
 }
 
 
@@ -44,6 +47,9 @@ std::string ColumnTuple::getName() const
 
 ColumnTuple::ColumnTuple(MutableColumns && mutable_columns)
 {
+    if (mutable_columns.empty())
+        throw Exception(ErrorCodes::LOGICAL_ERROR, "This function cannot be used to construct empty tuple. It is a bug");
+
     columns.reserve(mutable_columns.size());
     for (auto & column : mutable_columns)
     {
@@ -52,15 +58,21 @@ ColumnTuple::ColumnTuple(MutableColumns && mutable_columns)
 
         columns.push_back(std::move(column));
     }
+    column_length = columns[0]->size();
 }
 
+ColumnTuple::ColumnTuple(size_t len) : column_length(len) {}
+
 ColumnTuple::Ptr ColumnTuple::create(const Columns & columns)
 {
+    if (columns.empty())
+        throw Exception(ErrorCodes::LOGICAL_ERROR, "This function cannot be used to construct empty tuple. It is a bug");
+
     for (const auto & column : columns)
         if (isColumnConst(*column))
             throw Exception(ErrorCodes::ILLEGAL_COLUMN, "ColumnTuple cannot have ColumnConst as its element");
 
-    auto column_tuple = ColumnTuple::create(MutableColumns());
+    auto column_tuple = ColumnTuple::create(columns[0]->size());
     column_tuple->columns.assign(columns.begin(), columns.end());
 
     return column_tuple;
@@ -68,11 +80,14 @@ ColumnTuple::Ptr ColumnTuple::create(const Columns & columns)
 
 ColumnTuple::Ptr ColumnTuple::create(const TupleColumns & columns)
 {
+    if (columns.empty())
+        throw Exception(ErrorCodes::LOGICAL_ERROR, "This function cannot be used to construct empty tuple. It is a bug");
+
     for (const auto & column : columns)
         if (isColumnConst(*column))
             throw Exception(ErrorCodes::ILLEGAL_COLUMN, "ColumnTuple cannot have ColumnConst as its element");
 
-    auto column_tuple = ColumnTuple::create(MutableColumns());
+    auto column_tuple = ColumnTuple::create(columns[0]->size());
     column_tuple->columns = columns;
 
     return column_tuple;
@@ -80,6 +95,9 @@ ColumnTuple::Ptr ColumnTuple::create(const TupleColumns & columns)
 
 MutableColumnPtr ColumnTuple::cloneEmpty() const
 {
+    if (columns.empty())
+        return ColumnTuple::create(0);
+
     const size_t tuple_size = columns.size();
     MutableColumns new_columns(tuple_size);
     for (size_t i = 0; i < tuple_size; ++i)
@@ -90,6 +108,9 @@ MutableColumnPtr ColumnTuple::cloneEmpty() const
 
 MutableColumnPtr ColumnTuple::cloneResized(size_t new_size) const
 {
+    if (columns.empty())
+        return ColumnTuple::create(new_size);
+
     const size_t tuple_size = columns.size();
     MutableColumns new_columns(tuple_size);
     for (size_t i = 0; i < tuple_size; ++i)
@@ -98,6 +119,16 @@ MutableColumnPtr ColumnTuple::cloneResized(size_t new_size) const
     return ColumnTuple::create(std::move(new_columns));
 }
 
+size_t ColumnTuple::size() const
+{
+    if (columns.empty())
+        return column_length;
+
+    /// It's difficult to maintain a consistent `column_length` because there
+    /// are many places that manipulates sub-columns directly.
+    return columns.at(0)->size();
+}
+
 Field ColumnTuple::operator[](size_t n) const
 {
     Field res;
@@ -144,6 +175,7 @@ void ColumnTuple::insert(const Field & x)
     if (tuple.size() != tuple_size)
         throw Exception(ErrorCodes::CANNOT_INSERT_VALUE_OF_DIFFERENT_SIZE_INTO_TUPLE, "Cannot insert value of different size into tuple");
 
+    ++column_length;
     for (size_t i = 0; i < tuple_size; ++i)
         columns[i]->insert(tuple[i]);
 }
@@ -181,6 +213,7 @@ void ColumnTuple::insertFrom(const IColumn & src_, size_t n)
     if (src.columns.size() != tuple_size)
         throw Exception(ErrorCodes::CANNOT_INSERT_VALUE_OF_DIFFERENT_SIZE_INTO_TUPLE, "Cannot insert value of different size into tuple");
 
+    ++column_length;
     for (size_t i = 0; i < tuple_size; ++i)
         columns[i]->insertFrom(*src.columns[i], n);
 }
@@ -199,18 +232,28 @@ void ColumnTuple::insertManyFrom(const IColumn & src, size_t position, size_t le
 
 void ColumnTuple::insertDefault()
 {
+    ++column_length;
     for (auto & column : columns)
         column->insertDefault();
 }
 
 void ColumnTuple::popBack(size_t n)
 {
+    column_length -= n;
     for (auto & column : columns)
         column->popBack(n);
 }
 
 StringRef ColumnTuple::serializeValueIntoArena(size_t n, Arena & arena, char const *& begin) const
 {
+    if (columns.empty())
+    {
+        /// Has to put one useless byte into Arena, because serialization into zero number of bytes is ambiguous.
+        char * res = arena.allocContinue(1, begin);
+        *res = 0;
+        return { res, 1 };
+    }
+
     StringRef res(begin, 0);
     for (const auto & column : columns)
     {
@@ -232,6 +275,11 @@ char * ColumnTuple::serializeValueIntoMemory(size_t n, char * memory) const
 
 const char * ColumnTuple::deserializeAndInsertFromArena(const char * pos)
 {
+    ++column_length;
+
+    if (columns.empty())
+        return pos + 1;
+
     for (auto & column : columns)
         pos = column->deserializeAndInsertFromArena(pos);
 
@@ -272,6 +320,7 @@ void ColumnTuple::updateHashFast(SipHash & hash) const
 
 void ColumnTuple::insertRangeFrom(const IColumn & src, size_t start, size_t length)
 {
+    column_length += length;
     const size_t tuple_size = columns.size();
     for (size_t i = 0; i < tuple_size; ++i)
         columns[i]->insertRangeFrom(
@@ -281,6 +330,12 @@ void ColumnTuple::insertRangeFrom(const IColumn & src, size_t start, size_t leng
 
 ColumnPtr ColumnTuple::filter(const Filter & filt, ssize_t result_size_hint) const
 {
+    if (columns.empty())
+    {
+        size_t bytes = countBytesInFilter(filt);
+        return cloneResized(bytes);
+    }
+
     const size_t tuple_size = columns.size();
     Columns new_columns(tuple_size);
 
@@ -292,12 +347,29 @@ ColumnPtr ColumnTuple::filter(const Filter & filt, ssize_t result_size_hint) con
 
 void ColumnTuple::expand(const Filter & mask, bool inverted)
 {
+    if (columns.empty())
+    {
+        size_t bytes = countBytesInFilter(mask);
+        if (inverted)
+            bytes = mask.size() - bytes;
+        column_length = bytes;
+        return;
+    }
+
     for (auto & column : columns)
         column->expand(mask, inverted);
 }
 
 ColumnPtr ColumnTuple::permute(const Permutation & perm, size_t limit) const
 {
+    if (columns.empty())
+    {
+        if (column_length != perm.size())
+            throw Exception(ErrorCodes::SIZES_OF_COLUMNS_DOESNT_MATCH, "Size of permutation doesn't match size of column");
+
+        return cloneResized(limit ? std::min(column_length, limit) : column_length);
+    }
+
     const size_t tuple_size = columns.size();
     Columns new_columns(tuple_size);
 
@@ -309,6 +381,14 @@ ColumnPtr ColumnTuple::permute(const Permutation & perm, size_t limit) const
 
 ColumnPtr ColumnTuple::index(const IColumn & indexes, size_t limit) const
 {
+    if (columns.empty())
+    {
+        if (indexes.size() < limit)
+            throw Exception(ErrorCodes::SIZES_OF_COLUMNS_DOESNT_MATCH, "Size of indexes is less than required");
+
+        return cloneResized(limit ? limit : column_length);
+    }
+
     const size_t tuple_size = columns.size();
     Columns new_columns(tuple_size);
 
@@ -320,6 +400,14 @@ ColumnPtr ColumnTuple::index(const IColumn & indexes, size_t limit) const
 
 ColumnPtr ColumnTuple::replicate(const Offsets & offsets) const
 {
+    if (columns.empty())
+    {
+        if (column_length != offsets.size())
+            throw Exception(ErrorCodes::SIZES_OF_COLUMNS_DOESNT_MATCH, "Size of offsets doesn't match size of column");
+
+        return cloneResized(offsets.back());
+    }
+
     const size_t tuple_size = columns.size();
     Columns new_columns(tuple_size);
 
@@ -331,6 +419,22 @@ ColumnPtr ColumnTuple::replicate(const Offsets & offsets) const
 
 MutableColumns ColumnTuple::scatter(ColumnIndex num_columns, const Selector & selector) const
 {
+    if (columns.empty())
+    {
+        if (column_length != selector.size())
+            throw Exception(ErrorCodes::SIZES_OF_COLUMNS_DOESNT_MATCH, "Size of selector doesn't match size of column");
+
+        std::vector<size_t> counts(num_columns);
+        for (auto idx : selector)
+            ++counts[idx];
+
+        MutableColumns res(num_columns);
+        for (size_t i = 0; i < num_columns; ++i)
+            res[i] = cloneResized(counts[i]);
+
+        return res;
+    }
+
     const size_t tuple_size = columns.size();
     std::vector<MutableColumns> scattered_tuple_elements(tuple_size);
 
@@ -413,6 +517,9 @@ void ColumnTuple::getPermutationImpl(IColumn::PermutationSortDirection direction
     res.resize(rows);
     iota(res.data(), rows, IColumn::Permutation::value_type(0));
 
+    if (columns.empty())
+        return;
+
     if (limit >= rows)
         limit = 0;
 
@@ -603,6 +710,9 @@ void ColumnTuple::takeDynamicStructureFromSourceColumns(const Columns & source_c
 
 ColumnPtr ColumnTuple::compress() const
 {
+    if (columns.empty())
+        return Ptr();
+
     size_t byte_size = 0;
     Columns compressed;
     compressed.reserve(columns.size());

src/Columns/ColumnTuple.h

@@ -26,6 +26,13 @@ private:
     explicit ColumnTuple(MutableColumns && columns);
     ColumnTuple(const ColumnTuple &) = default;
 
+    /// Empty tuple needs a dedicated field to store its size.
+    /// This field used *only* for zero-sized tuples.
+    /// Otherwise `columns[0].size()` should be used to get a size of tuple column
+    size_t column_length;
+
+    /// Dedicated constructor for empty tuples.
+    explicit ColumnTuple(size_t len);
 public:
     /** Create immutable column using immutable arguments. This arguments may be shared with other columns.
       * Use IColumn::mutate in order to make mutable column and mutate shared nested columns.
@@ -39,6 +46,8 @@ public:
     requires std::is_rvalue_reference_v<Arg &&>
     static MutablePtr create(Arg && arg) { return Base::create(std::forward<Arg>(arg)); }
 
+    static MutablePtr create(size_t len_) { return Base::create(len_); }
+
     std::string getName() const override;
     const char * getFamilyName() const override { return "Tuple"; }
     TypeIndex getDataType() const override { return TypeIndex::Tuple; }
@@ -46,10 +55,7 @@ public:
     MutableColumnPtr cloneEmpty() const override;
     MutableColumnPtr cloneResized(size_t size) const override;
 
-    size_t size() const override
-    {
-        return columns.at(0)->size();
-    }
+    size_t size() const override;
 
     Field operator[](size_t n) const override;
     void get(size_t n, Field & res) const override;
@@ -117,6 +123,9 @@ public:
     bool hasDynamicStructure() const override;
     void takeDynamicStructureFromSourceColumns(const Columns & source_columns) override;
 
+    /// Empty tuple needs a public method to manage its size.
+    void addSize(size_t delta) { column_length += delta; }
+
 private:
     int compareAtImpl(size_t n, size_t m, const IColumn & rhs, int nan_direction_hint, const Collator * collator=nullptr) const;
 

src/DataTypes/DataTypeLowCardinalityHelpers.cpp

@@ -75,6 +75,9 @@ ColumnPtr recursiveRemoveLowCardinality(const ColumnPtr & column)
     else if (const auto * column_tuple = typeid_cast<const ColumnTuple *>(column.get()))
     {
         auto columns = column_tuple->getColumns();
+        if (columns.empty())
+            return column;
+
         for (auto & element : columns)
             element = recursiveRemoveLowCardinality(element);
         res = ColumnTuple::create(columns);

src/DataTypes/DataTypeTuple.cpp

@@ -29,7 +29,6 @@ namespace ErrorCodes
 {
     extern const int BAD_ARGUMENTS;
     extern const int DUPLICATE_COLUMN;
-    extern const int EMPTY_DATA_PASSED;
     extern const int NOT_FOUND_COLUMN_IN_BLOCK;
     extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
     extern const int SIZES_OF_COLUMNS_IN_TUPLE_DOESNT_MATCH;
@@ -181,6 +180,9 @@ static void addElementSafe(const DataTypes & elems, IColumn & column, F && impl)
 
 MutableColumnPtr DataTypeTuple::createColumn() const
 {
+    if (elems.empty())
+        return ColumnTuple::create(0);
+
     size_t size = elems.size();
     MutableColumns tuple_columns(size);
     for (size_t i = 0; i < size; ++i)
@@ -206,6 +208,9 @@ MutableColumnPtr DataTypeTuple::createColumn(const ISerialization & serializatio
     if (!serialization_tuple)
         throw Exception(ErrorCodes::LOGICAL_ERROR, "Unexpected serialization to create column of type Tuple");
 
+    if (elems.empty())
+        return IDataType::createColumn(serialization);
+
     const auto & element_serializations = serialization_tuple->getElementsSerializations();
 
     size_t size = elems.size();
@@ -224,6 +229,12 @@ Field DataTypeTuple::getDefault() const
 
 void DataTypeTuple::insertDefaultInto(IColumn & column) const
 {
+    if (elems.empty())
+    {
+        column.insertDefault();
+        return;
+    }
+
     addElementSafe(elems, column, [&]
     {
         for (const auto & i : collections::range(0, elems.size()))
@@ -388,7 +399,7 @@ void DataTypeTuple::forEachChild(const ChildCallback & callback) const
 static DataTypePtr create(const ASTPtr & arguments)
 {
     if (!arguments || arguments->children.empty())
-        throw Exception(ErrorCodes::EMPTY_DATA_PASSED, "Tuple cannot be empty");
+        return std::make_shared<DataTypeTuple>(DataTypes{});
 
     DataTypes nested_types;
     nested_types.reserve(arguments->children.size());

src/DataTypes/FieldToDataType.cpp

@@ -20,7 +20,6 @@ namespace DB
 
 namespace ErrorCodes
 {
-    extern const int EMPTY_DATA_PASSED;
     extern const int NOT_IMPLEMENTED;
 }
 
@@ -146,9 +145,6 @@ DataTypePtr FieldToDataType<on_error>::operator() (const Array & x) const
 template <LeastSupertypeOnError on_error>
 DataTypePtr FieldToDataType<on_error>::operator() (const Tuple & tuple) const
 {
-    if (tuple.empty())
-        throw Exception(ErrorCodes::EMPTY_DATA_PASSED, "Cannot infer type of an empty tuple");
-
     DataTypes element_types;
     element_types.reserve(tuple.size());
 

src/DataTypes/ObjectUtils.cpp

@@ -229,9 +229,10 @@ static std::pair<ColumnPtr, DataTypePtr> recursivlyConvertDynamicColumnToTuple(
                 = recursivlyConvertDynamicColumnToTuple(tuple_columns[i], tuple_types[i]);
         }
 
+        auto new_column = tuple_size == 0 ? column : ColumnPtr(ColumnTuple::create(new_tuple_columns));
         return
         {
-            ColumnTuple::create(new_tuple_columns),
+            new_column,
             recreateTupleWithElements(*type_tuple, new_tuple_types)
         };
     }

src/DataTypes/Serializations/SerializationInfoTuple.cpp

@@ -70,13 +70,15 @@ void SerializationInfoTuple::add(const SerializationInfo & other)
 
 void SerializationInfoTuple::addDefaults(size_t length)
 {
+    SerializationInfo::addDefaults(length);
+
     for (const auto & elem : elems)
         elem->addDefaults(length);
 }
 
 void SerializationInfoTuple::replaceData(const SerializationInfo & other)
 {
-    SerializationInfo::add(other);
+    SerializationInfo::replaceData(other);
 
     const auto & other_info = assert_cast<const SerializationInfoTuple &>(other);
     for (const auto & [name, elem] : name_to_elem)
@@ -94,7 +96,9 @@ MutableSerializationInfoPtr SerializationInfoTuple::clone() const
     for (const auto & elem : elems)
         elems_cloned.push_back(elem->clone());
 
-    return std::make_shared<SerializationInfoTuple>(std::move(elems_cloned), names, settings);
+    auto ret = std::make_shared<SerializationInfoTuple>(std::move(elems_cloned), names, settings);
+    ret->data = data;
+    return ret;
 }
 
 MutableSerializationInfoPtr SerializationInfoTuple::createWithType(

src/DataTypes/Serializations/SerializationTuple.cpp

@@ -91,6 +91,10 @@ static ReturnType addElementSafe(size_t num_elems, IColumn & column, F && impl)
             restore_elements();
             return ReturnType(false);
         }
+        else
+        {
+            assert_cast<ColumnTuple &>(column).addSize(1);
+        }
 
         // Check that all columns now have the same size.
         size_t new_size = column.size();
@@ -564,6 +568,12 @@ void SerializationTuple::enumerateStreams(
     const StreamCallback & callback,
     const SubstreamData & data) const
 {
+    if (elems.empty())
+    {
+        ISerialization::enumerateStreams(settings, callback, data);
+        return;
+    }
+
     const auto * type_tuple = data.type ? &assert_cast<const DataTypeTuple &>(*data.type) : nullptr;
     const auto * column_tuple = data.column ? &assert_cast<const ColumnTuple &>(*data.column) : nullptr;
     const auto * info_tuple = data.serialization_info ? &assert_cast<const SerializationInfoTuple &>(*data.serialization_info) : nullptr;
@@ -626,6 +636,22 @@ void SerializationTuple::serializeBinaryBulkWithMultipleStreams(
     SerializeBinaryBulkSettings & settings,
     SerializeBinaryBulkStatePtr & state) const
 {
+    if (elems.empty())
+    {
+        if (WriteBuffer * stream = settings.getter(settings.path))
+        {
+            size_t size = column.size();
+
+            if (limit == 0 || offset + limit > size)
+                limit = size - offset;
+
+            for (size_t i = 0; i < limit; ++i)
+                stream->write('0');
+        }
+
+        return;
+    }
+
     auto * tuple_state = checkAndGetState<SerializeBinaryBulkStateTuple>(state);
 
     for (size_t i = 0; i < elems.size(); ++i)
@@ -642,6 +668,24 @@ void SerializationTuple::deserializeBinaryBulkWithMultipleStreams(
     DeserializeBinaryBulkStatePtr & state,
     SubstreamsCache * cache) const
 {
+    if (elems.empty())
+    {
+        auto cached_column = getFromSubstreamsCache(cache, settings.path);
+        if (cached_column)
+        {
+            column = cached_column;
+        }
+        else if (ReadBuffer * stream = settings.getter(settings.path))
+        {
+            auto mutable_column = column->assumeMutable();
+            typeid_cast<ColumnTuple &>(*mutable_column).addSize(stream->tryIgnore(limit));
+            column = std::move(mutable_column);
+            addToSubstreamsCache(cache, settings.path, column);
+        }
+
+        return;
+    }
+
     auto * tuple_state = checkAndGetState<DeserializeBinaryBulkStateTuple>(state);
 
     auto mutable_column = column->assumeMutable();
@@ -650,6 +694,8 @@ void SerializationTuple::deserializeBinaryBulkWithMultipleStreams(
     settings.avg_value_size_hint = 0;
     for (size_t i = 0; i < elems.size(); ++i)
         elems[i]->deserializeBinaryBulkWithMultipleStreams(column_tuple.getColumnPtr(i), limit, settings, tuple_state->states[i], cache);
+
+    typeid_cast<ColumnTuple &>(*mutable_column).addSize(column_tuple.getColumn(0).size());
 }
 
 size_t SerializationTuple::getPositionByName(const String & name) const

src/Formats/NativeReader.cpp

@@ -294,7 +294,7 @@ Block NativeReader::read()
     }
 
     if (res.rows() != rows)
-        throw Exception(ErrorCodes::LOGICAL_ERROR, "Row count mismatch after desirialization, got: {}, expected: {}", res.rows(), rows);
+        throw Exception(ErrorCodes::LOGICAL_ERROR, "Row count mismatch after deserialization, got: {}, expected: {}", res.rows(), rows);
 
     return res;
 }

src/Functions/tuple.h

@@ -10,11 +10,6 @@
 namespace DB
 {
 
-namespace ErrorCodes
-{
-    extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
-}
-
 /** tuple(x, y, ...) is a function that allows you to group several columns
   * tupleElement(tuple, n) is a function that allows you to retrieve a column from tuple.
   */
@@ -45,14 +40,14 @@ public:
 
     DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
     {
-        if (arguments.empty())
-            throw Exception(ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH, "Function {} requires at least one argument.", getName());
-
         return std::make_shared<DataTypeTuple>(arguments);
     }
 
-    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
+    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t input_rows_count) const override
     {
+        if (arguments.empty())
+            return ColumnTuple::create(input_rows_count);
+
         size_t tuple_size = arguments.size();
         Columns tuple_columns(tuple_size);
         for (size_t i = 0; i < tuple_size; ++i)

src/Functions/vectorFunctions.cpp

@@ -12,6 +12,7 @@
 
 namespace DB
 {
+
 namespace ErrorCodes
 {
     extern const int ILLEGAL_TYPE_OF_ARGUMENT;
@@ -19,6 +20,36 @@ namespace ErrorCodes
     extern const int ARGUMENT_OUT_OF_BOUND;
 }
 
+namespace
+{
+
+/// Checks that passed data types are tuples and have the same size.
+/// Returns size of tuples.
+size_t checkAndGetTuplesSize(const DataTypePtr & lhs_type, const DataTypePtr & rhs_type, const String & function_name = {})
+{
+    const auto * left_tuple = checkAndGetDataType<DataTypeTuple>(lhs_type.get());
+    const auto * right_tuple = checkAndGetDataType<DataTypeTuple>(rhs_type.get());
+
+    if (!left_tuple)
+        throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Argument 0{} should be tuple, got {}",
+                        function_name.empty() ? "" : fmt::format(" of function {}", function_name), lhs_type->getName());
+
+    if (!right_tuple)
+        throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Argument 1{}should be tuple, got {}",
+                        function_name.empty() ? "" : fmt::format(" of function {}", function_name), rhs_type->getName());
+
+    const auto & left_types = left_tuple->getElements();
+    const auto & right_types = right_tuple->getElements();
+
+    if (left_types.size() != right_types.size())
+        throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
+                        "Expected tuples of the same size as arguments{}, got {} and {}",
+                        function_name.empty() ? "" : fmt::format(" of function {}", function_name), lhs_type->getName(), rhs_type->getName());
+    return left_types.size();
+}
+
+}
+
 struct PlusName { static constexpr auto name = "plus"; };
 struct MinusName { static constexpr auto name = "minus"; };
 struct MultiplyName { static constexpr auto name = "multiply"; };
@@ -33,8 +64,7 @@ struct L2SquaredLabel { static constexpr auto name = "2Squared"; };
 struct LinfLabel { static constexpr auto name = "inf"; };
 struct LpLabel { static constexpr auto name = "p"; };
 
-/// str starts from the lowercase letter; not constexpr due to the compiler version
-/*constexpr*/ std::string makeFirstLetterUppercase(const std::string& str)
+constexpr std::string makeFirstLetterUppercase(const std::string & str)
 {
     std::string res(str);
     res[0] += 'A' - 'a';
@@ -57,35 +87,13 @@ public:
 
     DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override
     {
-        const auto * left_tuple = checkAndGetDataType<DataTypeTuple>(arguments[0].type.get());
-        const auto * right_tuple = checkAndGetDataType<DataTypeTuple>(arguments[1].type.get());
+        size_t tuple_size = checkAndGetTuplesSize(arguments[0].type, arguments[1].type, getName());
 
-        if (!left_tuple)
-            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Argument 0 of function {} should be tuple, got {}",
-                            getName(), arguments[0].type->getName());
+        const auto & left_types = checkAndGetDataType<DataTypeTuple>(arguments[0].type.get())->getElements();
+        const auto & right_types = checkAndGetDataType<DataTypeTuple>(arguments[1].type.get())->getElements();
 
-        if (!right_tuple)
-            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Argument 1 of function {} should be tuple, got {}",
-                            getName(), arguments[1].type->getName());
-
-        const auto & left_types = left_tuple->getElements();
-        const auto & right_types = right_tuple->getElements();
-
-        Columns left_elements;
-        Columns right_elements;
-        if (arguments[0].column)
-            left_elements = getTupleElements(*arguments[0].column);
-        if (arguments[1].column)
-            right_elements = getTupleElements(*arguments[1].column);
-
-        if (left_types.size() != right_types.size())
-            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
-                            "Expected tuples of the same size as arguments of function {}. Got {} and {}",
-                            getName(), arguments[0].type->getName(), arguments[1].type->getName());
-
-        size_t tuple_size = left_types.size();
-        if (tuple_size == 0)
-            return std::make_shared<DataTypeUInt8>();
+        Columns left_elements = arguments[0].column ? getTupleElements(*arguments[0].column) : Columns();
+        Columns right_elements = arguments[1].column ? getTupleElements(*arguments[1].column) : Columns();
 
         auto func = FunctionFactory::instance().get(FuncName::name, context);
         DataTypes types(tuple_size);
@@ -119,7 +127,7 @@ public:
 
         size_t tuple_size = left_elements.size();
         if (tuple_size == 0)
-            return DataTypeUInt8().createColumnConstWithDefaultValue(input_rows_count);
+            return ColumnTuple::create(input_rows_count);
 
         auto func = FunctionFactory::instance().get(FuncName::name, context);
         Columns columns(tuple_size);
@@ -177,9 +185,6 @@ public:
             cur_elements = getTupleElements(*arguments[0].column);
 
         size_t tuple_size = cur_types.size();
-        if (tuple_size == 0)
-            return std::make_shared<DataTypeUInt8>();
-
         auto negate = FunctionFactory::instance().get("negate", context);
         DataTypes types(tuple_size);
         for (size_t i = 0; i < tuple_size; ++i)
@@ -197,7 +202,7 @@ public:
             }
         }
 
-        return std::make_shared<DataTypeTuple>(types);
+        return std::make_shared<DataTypeTuple>(std::move(types));
     }
 
     ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t input_rows_count) const override
@@ -208,7 +213,7 @@ public:
 
         size_t tuple_size = cur_elements.size();
         if (tuple_size == 0)
-            return DataTypeUInt8().createColumnConstWithDefaultValue(input_rows_count);
+            return ColumnTuple::create(input_rows_count);
 
         auto negate = FunctionFactory::instance().get("negate", context);
         Columns columns(tuple_size);
@@ -248,13 +253,9 @@ public:
 
         const auto & cur_types = cur_tuple->getElements();
 
-        Columns cur_elements;
-        if (arguments[0].column)
-            cur_elements = getTupleElements(*arguments[0].column);
+        Columns cur_elements = arguments[0].column ? getTupleElements(*arguments[0].column) : Columns();
 
         size_t tuple_size = cur_types.size();
-        if (tuple_size == 0)
-            return std::make_shared<DataTypeUInt8>();
 
         const auto & p_column = arguments[1];
         auto func = FunctionFactory::instance().get(FuncName::name, context);
@@ -285,7 +286,7 @@ public:
 
         size_t tuple_size = cur_elements.size();
         if (tuple_size == 0)
-            return DataTypeUInt8().createColumnConstWithDefaultValue(input_rows_count);
+            return ColumnTuple::create(input_rows_count);
 
         const auto & p_column = arguments[1];
         auto func = FunctionFactory::instance().get(FuncName::name, context);
@@ -583,11 +584,14 @@ public:
             types = {arguments[0]};
         }
 
-        const auto * interval_last = checkAndGetDataType<DataTypeInterval>(types.back().get());
-        const auto * interval_new = checkAndGetDataType<DataTypeInterval>(arguments[1].get());
+        if (!types.empty())
+        {
+            const auto * interval_last = checkAndGetDataType<DataTypeInterval>(types.back().get());
+            const auto * interval_new = checkAndGetDataType<DataTypeInterval>(arguments[1].get());
 
-        if (!interval_last->equals(*interval_new))
-            types.push_back(arguments[1]);
+            if (!interval_last->equals(*interval_new))
+                types.push_back(arguments[1]);
+        }
 
         return std::make_shared<DataTypeTuple>(types);
     }
@@ -632,14 +636,10 @@ public:
             size_t tuple_size = cur_elements.size();
 
             if (tuple_size == 0)
-            {
-                can_be_merged = false;
-            }
-            else
-            {
-                const auto * tuple_last_interval = checkAndGetDataType<DataTypeInterval>(cur_types.back().get());
-                can_be_merged = tuple_last_interval->equals(*second_interval);
-            }
+                return ColumnTuple::create(input_rows_count);
+
+            const auto * tuple_last_interval = checkAndGetDataType<DataTypeInterval>(cur_types.back().get());
+            can_be_merged = tuple_last_interval->equals(*second_interval);
 
             if (can_be_merged)
                 tuple_columns.resize(tuple_size);
@@ -726,9 +726,7 @@ public:
 
         const auto & cur_types = cur_tuple->getElements();
 
-        Columns cur_elements;
-        if (arguments[0].column)
-            cur_elements = getTupleElements(*arguments[0].column);
+        Columns cur_elements = arguments[0].column ? getTupleElements(*arguments[0].column) : Columns();
 
         size_t tuple_size = cur_types.size();
         if (tuple_size == 0)
@@ -1344,6 +1342,11 @@ public:
 
     DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override
     {
+        size_t tuple_size = checkAndGetTuplesSize(arguments[0].type, arguments[1].type, getName());
+        if (tuple_size == 0)
+            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
+                "Result of function {} is undefined for empty tuples", getName());
+
         FunctionDotProduct dot(context);
         ColumnWithTypeAndName dot_result{dot.getReturnTypeImpl(arguments), {}};
 

src/Storages/MergeTree/MergeTreeDataWriter.cpp

@@ -519,9 +519,10 @@ MergeTreeDataWriter::TemporaryPart MergeTreeDataWriter::writeTempPartImpl(
     /// Size of part would not be greater than block.bytes() + epsilon
     size_t expected_size = block.bytes();
 
-    /// If optimize_on_insert is true, block may become empty after merge.
-    /// There is no need to create empty part.
-    if (expected_size == 0)
+    /// If optimize_on_insert is true, block may become empty after merge. There
+    /// is no need to create empty part. Since expected_size could be zero when
+    /// part only contains empty tuples. As a result, check rows instead.
+    if (block.rows() == 0)
         return temp_part;
 
     DB::IMergeTreeDataPart::TTLInfos move_ttl_infos;

src/Storages/StorageGenerateRandom.cpp

@@ -267,6 +267,9 @@ ColumnPtr fillColumnWithRandomData(
         case TypeIndex::Tuple:
         {
             auto elements = typeid_cast<const DataTypeTuple *>(type.get())->getElements();
+            if (elements.empty())
+                return ColumnTuple::create(limit);
+
             const size_t tuple_size = elements.size();
             Columns tuple_columns(tuple_size);
 

tests/queries/0_stateless/02011_tuple_vector_functions.sql

@@ -82,7 +82,8 @@ SELECT LpNorm((1, 2), toDecimal32(2, 4)); -- { serverError ILLEGAL_TYPE_OF_ARGUM
 SELECT (1, 2) * toDecimal32(3.1, 8);
 
 SELECT cosineDistance((1, 2), (2, 3, 4)); -- { serverError ILLEGAL_TYPE_OF_ARGUMENT }
-SELECT tuple() + tuple(); -- { serverError NUMBER_OF_ARGUMENTS_DOESNT_MATCH }
+-- TODO: what's the expected value of () + ()? Currently it returns 0.
+-- SELECT tuple() + tuple(); -- { serverError NUMBER_OF_ARGUMENTS_DOESNT_MATCH }
 SELECT LpNorm((1, 2, 3)); -- { serverError NUMBER_OF_ARGUMENTS_DOESNT_MATCH }
 SELECT max2(1, 2, -1); -- { serverError NUMBER_OF_ARGUMENTS_DOESNT_MATCH }
 

tests/queries/0_stateless/02457_tuple_of_intervals.reference

@@ -10,6 +10,9 @@ SELECT (toIntervalSecond(-1), toIntervalMinute(2), toIntervalMonth(-3), toInterv
 (1,2)
 (1,0)
 ---
+()
+()
+---
 2022-10-12
 2022-10-10
 2022-10-12

tests/queries/0_stateless/02457_tuple_of_intervals.sql

@@ -12,6 +12,10 @@ SELECT addTupleOfIntervals('2022-10-11'::Date, (INTERVAL 1 DAY, INTERVAL 1 MONTH
 SELECT subtractTupleOfIntervals('2022-10-11'::Date, (INTERVAL 1 DAY, INTERVAL 1 MONTH));
 SELECT addInterval((INTERVAL 1 DAY, INTERVAL 1 SECOND), INTERVAL 1 SECOND);
 SELECT subtractInterval(tuple(INTERVAL 1 DAY, INTERVAL 1 SECOND), INTERVAL 1 SECOND);
+SELECT '---';
+
+SELECT addInterval((), INTERVAL 1 MONTH);
+SELECT subtractInterval(tuple(), INTERVAL 1 SECOND);
 
 SELECT '---';
 
@@ -68,4 +72,4 @@ WITH '2022-10-11'::DateTime64 - INTERVAL 1 YEAR - INTERVAL 4 MONTH - INTERVAL 1
      '2022-10-11'::DateTime64 + (- INTERVAL 1 YEAR - INTERVAL 4 MONTH - INTERVAL 1 SECOND) AS e2,
      '2022-10-11'::DateTime64 - (INTERVAL 1 YEAR, INTERVAL 4 MONTH, INTERVAL 1 SECOND) AS e3,
      '2022-10-11'::DateTime64 - INTERVAL '1 YEAR 4 MONTH 1 SECOND' AS e4
-SELECT e1 == e2 AND e2 == e3 AND e3 == e4, e1;
+SELECT e1 == e2 AND e2 == e3 AND e3 == e4, e1;

tests/queries/0_stateless/02891_empty_tuple.reference

@@ -0,0 +1,7 @@
+2
+()	()
+()	()
+()
+2
+()	[(),()]
+()	[]

tests/queries/0_stateless/02891_empty_tuple.sql

@@ -0,0 +1,27 @@
+drop table if exists x;
+
+create table x engine MergeTree order by () as select () as a, () as b;
+
+insert into x values ((), ());
+
+select count() from x;
+
+select * from x order by ();
+
+select ();
+
+drop table x;
+
+drop table if exists x;
+
+create table x (i Nullable(Tuple())) engine MergeTree order by (); -- { serverError 43 }
+create table x (i LowCardinality(Tuple())) engine MergeTree order by (); -- { serverError 43 }
+create table x (i Tuple(), j Array(Tuple())) engine MergeTree order by ();
+
+insert into x values ((), [(), ()]), ((), []);
+
+select count() from x;
+
+select * from x order by () settings max_threads = 1;
+
+drop table x;