ClickHouse/dbms/src/AggregateFunctions/AggregateFunctionGroupUniqArray.h

#pragma once

#include <IO/WriteHelpers.h>
#include <IO/ReadHelpers.h>

#include <DataTypes/DataTypeArray.h>
#include <DataTypes/DataTypesNumber.h>
#include <DataTypes/DataTypeString.h>

#include <Columns/ColumnArray.h>

#include <Common/HashTable/HashSet.h>

#include <AggregateFunctions/IAggregateFunction.h>

#define AGGREGATE_FUNCTION_GROUP_ARRAY_UNIQ_MAX_SIZE 0xFFFFFF


namespace DB
{


template <typename T>
struct AggregateFunctionGroupUniqArrayData
{
    /// When creating, the hash table must be small.
    using Set = HashSet<
        T,
        DefaultHash<T>,
        HashTableGrower<4>,
        HashTableAllocatorWithStackMemory<sizeof(T) * (1 << 4)>
    >;

    Set value;
};


/// Puts all values to the hash set. Returns an array of unique values. Implemented for numeric types.
template <typename T>
class AggregateFunctionGroupUniqArray
    : public IAggregateFunctionDataHelper<AggregateFunctionGroupUniqArrayData<T>, AggregateFunctionGroupUniqArray<T>>
{
private:
    using State = AggregateFunctionGroupUniqArrayData<T>;

public:
    String getName() const override { return "groupUniqArray"; }

    DataTypePtr getReturnType() const override
    {
        return std::make_shared<DataTypeArray>(std::make_shared<DataTypeNumber<T>>());
    }

    void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num, Arena *) const override
    {
        this->data(place).value.insert(static_cast<const ColumnVector<T> &>(*columns[0]).getData()[row_num]);
    }

    void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs, Arena *) const override
    {
        this->data(place).value.merge(this->data(rhs).value);
    }

    void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
    {
        auto & set = this->data(place).value;
        size_t size = set.size();
        writeVarUInt(size, buf);
        for (auto & elem : set)
            writeIntBinary(elem, buf);
    }

    void deserialize(AggregateDataPtr place, ReadBuffer & buf, Arena *) const override
    {
        this->data(place).value.read(buf);
    }

    void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
    {
        ColumnArray & arr_to = static_cast<ColumnArray &>(to);
        ColumnArray::Offsets & offsets_to = arr_to.getOffsets();

        const typename State::Set & set = this->data(place).value;
        size_t size = set.size();

        offsets_to.push_back((offsets_to.size() == 0 ? 0 : offsets_to.back()) + size);

        typename ColumnVector<T>::Container & data_to = static_cast<ColumnVector<T> &>(arr_to.getData()).getData();
        size_t old_size = data_to.size();
        data_to.resize(old_size + size);

        size_t i = 0;
        for (auto it = set.begin(); it != set.end(); ++it, ++i)
            data_to[old_size + i] = *it;
    }

    const char * getHeaderFilePath() const override { return __FILE__; }
};


/// Generic implementation, it uses serialized representation as object descriptor.
struct AggreagteFunctionGroupUniqArrayGenericData
{
    static constexpr size_t INIT_ELEMS = 2; /// adjustable
    static constexpr size_t ELEM_SIZE = sizeof(HashSetCellWithSavedHash<StringRef, StringRefHash>);
    using Set = HashSetWithSavedHash<StringRef, StringRefHash, HashTableGrower<INIT_ELEMS>, HashTableAllocatorWithStackMemory<INIT_ELEMS * ELEM_SIZE>>;

    Set value;
};

/** Template parameter with true value should be used for columns that store their elements in memory continuously.
 *  For such columns groupUniqArray() can be implemented more efficently (especially for small numeric arrays).
 */
template <bool is_plain_column = false>
class AggreagteFunctionGroupUniqArrayGeneric
    : public IAggregateFunctionDataHelper<AggreagteFunctionGroupUniqArrayGenericData, AggreagteFunctionGroupUniqArrayGeneric<is_plain_column>>
{
    DataTypePtr input_data_type;

    using State = AggreagteFunctionGroupUniqArrayGenericData;

    static StringRef getSerialization(const IColumn & column, size_t row_num, Arena & arena);

    static void deserializeAndInsert(StringRef str, IColumn & data_to);

public:
    AggreagteFunctionGroupUniqArrayGeneric(const DataTypePtr & input_data_type)
        : input_data_type(input_data_type) {}

    String getName() const override { return "groupUniqArray"; }

    DataTypePtr getReturnType() const override
    {
        return std::make_shared<DataTypeArray>(input_data_type);
    }

    bool allocatesMemoryInArena() const override
    {
        return true;
    }

    void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
    {
        auto & set = this->data(place).value;
        writeVarUInt(set.size(), buf);

        for (const auto & elem : set)
        {
            writeStringBinary(elem, buf);
        }
    }

    void deserialize(AggregateDataPtr place, ReadBuffer & buf, Arena * arena) const override
    {
        auto & set = this->data(place).value;
        size_t size;
        readVarUInt(size, buf);
        //TODO: set.reserve(size);

        for (size_t i = 0; i < size; ++i)
        {
            set.insert(readStringBinaryInto(*arena, buf));
        }
    }

    void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num, Arena * arena) const override
    {
        auto & set = this->data(place).value;

        bool inserted;
        State::Set::iterator it;

        StringRef str_serialized = getSerialization(*columns[0], row_num, *arena);
        set.emplace(str_serialized, it, inserted);

        if constexpr (!is_plain_column)
        {
            if (!inserted)
                arena->rollback(str_serialized.size);
        }
        else
        {
            if (inserted)
                it->data = arena->insert(str_serialized.data, str_serialized.size);
        }
    }

    void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs, Arena * arena) const override
    {
        auto & cur_set = this->data(place).value;
        auto & rhs_set = this->data(rhs).value;

        bool inserted;
        State::Set::iterator it;
        for (auto & rhs_elem : rhs_set)
        {
            cur_set.emplace(rhs_elem, it, inserted);
            if (inserted)
                it->data = arena->insert(it->data, it->size);
        }
    }

    void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
    {
        ColumnArray & arr_to = static_cast<ColumnArray &>(to);
        ColumnArray::Offsets & offsets_to = arr_to.getOffsets();
        IColumn & data_to = arr_to.getData();

        auto & set = this->data(place).value;
        offsets_to.push_back((offsets_to.size() == 0 ? 0 : offsets_to.back()) + set.size());

        for (auto & elem : set)
        {
            deserializeAndInsert(elem, data_to);
        }
    }

    const char * getHeaderFilePath() const override { return __FILE__; }
};


template <>
inline StringRef AggreagteFunctionGroupUniqArrayGeneric<false>::getSerialization(const IColumn & column, size_t row_num, Arena & arena)
{
    const char * begin = nullptr;
    return column.serializeValueIntoArena(row_num, arena, begin);
}

template <>
inline StringRef AggreagteFunctionGroupUniqArrayGeneric<true>::getSerialization(const IColumn & column, size_t row_num, Arena &)
{
    return column.getDataAt(row_num);
}

template <>
inline void AggreagteFunctionGroupUniqArrayGeneric<false>::deserializeAndInsert(StringRef str, IColumn & data_to)
{
    data_to.deserializeAndInsertFromArena(str.data);
}

template <>
inline void AggreagteFunctionGroupUniqArrayGeneric<true>::deserializeAndInsert(StringRef str, IColumn & data_to)
{
    data_to.insertData(str.data, str.size);
}


#undef AGGREGATE_FUNCTION_GROUP_ARRAY_UNIQ_MAX_SIZE

}