ClickHouse/dbms/include/DB/AggregateFunctions/AggregateFunctionAvg.h
2017-03-09 01:56:38 +01:00

78 lines
1.9 KiB
C++

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