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/DataTypesNumberFixed.h>
#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) {}
};
/// Считает арифметическое среднее значение чисел.
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 new DataTypeFloat64;
}
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);
}
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void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) 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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}
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void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) 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 deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const override
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{
typename NearestFieldType<T>::Type tmp_sum = 0;
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UInt64 tmp_count = 0;
readBinary(tmp_sum, buf);
readVarUInt(tmp_count, buf);
this->data(place).sum += tmp_sum;
this->data(place).count += tmp_count;
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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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}