ClickHouse/dbms/src/AggregateFunctions/AggregateFunctionSum.h

#pragma once

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

#include <DataTypes/DataTypesNumber.h>
#include <Columns/ColumnVector.h>

#include <AggregateFunctions/IUnaryAggregateFunction.h>


namespace DB
{

template <typename T>
struct AggregateFunctionSumData
{
    T sum;

    AggregateFunctionSumData() : sum(0) {}
};


/// Counts the sum of the numbers.
template <typename T>
class AggregateFunctionSum final : public IUnaryAggregateFunction<AggregateFunctionSumData<typename NearestFieldType<T>::Type>, AggregateFunctionSum<T> >
{
public:
    String getName() const override { return "sum"; }

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

    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 addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num, Arena *) const
    {
        this->data(place).sum += static_cast<const ColumnVector<T> &>(column).getData()[row_num];
    }

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

    void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
    {
        writeBinary(this->data(place).sum, buf);
    }

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

    void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
    {
        static_cast<ColumnVector<typename NearestFieldType<T>::Type> &>(to).getData().push_back(this->data(place).sum);
    }
};


}