ClickHouse/dbms/include/DB/AggregateFunctions/AggregateFunctionAvg.h

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#pragma once
#include <DB/IO/WriteHelpers.h>
#include <DB/IO/ReadHelpers.h>
#include <DB/DataTypes/DataTypesNumber.h>
#include <DB/Columns/ColumnsNumber.h>
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#include <DB/AggregateFunctions/IUnaryAggregateFunction.h>
namespace DB
{
template <typename T>
struct AggregateFunctionAvgData
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{
T sum;
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UInt64 count;
AggregateFunctionAvgData() : sum(0), count(0) {}
};
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/// Calculates arithmetic mean of numbers.
template <typename T>
class AggregateFunctionAvg final : public IUnaryAggregateFunction<AggregateFunctionAvgData<typename NearestFieldType<T>::Type>, AggregateFunctionAvg<T> >
{
public:
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String getName() const override { return "avg"; }
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DataTypePtr getReturnType() const override
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{
return std::make_shared<DataTypeFloat64>();
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}
void setArgument(const DataTypePtr & argument)
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{
if (!argument->isNumeric())
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
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{
this->data(place).sum += static_cast<const ColumnVector<T> &>(column).getData()[row_num];
++this->data(place).count;
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}
void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs, Arena * arena) const override
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{
this->data(place).sum += this->data(rhs).sum;
this->data(place).count += this->data(rhs).count;
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}
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void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
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{
writeBinary(this->data(place).sum, buf);
writeVarUInt(this->data(place).count, buf);
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}
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void deserialize(AggregateDataPtr place, ReadBuffer & buf, Arena *) const override
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{
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readBinary(this->data(place).sum, buf);
readVarUInt(this->data(place).count, buf);
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}
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void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
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{
static_cast<ColumnFloat64 &>(to).getData().push_back(
static_cast<Float64>(this->data(place).sum) / this->data(place).count);
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}
};
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}