ClickHouse/dbms/AggregateFunctions/AggregateFunctionAvg.h

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#pragma once
#include <IO/ReadHelpers.h>
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#include <IO/WriteHelpers.h>
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#include <Columns/ColumnsNumber.h>
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#include <DataTypes/DataTypesDecimal.h>
#include <DataTypes/DataTypesNumber.h>
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#include <AggregateFunctions/IAggregateFunction.h>
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namespace DB
{
namespace ErrorCodes
{
}
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template <typename T, typename Denominator>
struct AggregateFunctionAvgData
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{
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T numerator = 0;
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Denominator denominator = 0;
template <typename ResultT>
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ResultT NO_SANITIZE_UNDEFINED result() const
{
if constexpr (std::is_floating_point_v<ResultT>)
if constexpr (std::numeric_limits<ResultT>::is_iec559)
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return static_cast<ResultT>(numerator) / denominator; /// allow division by zero
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if (denominator == 0)
return static_cast<ResultT>(0);
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return static_cast<ResultT>(numerator / denominator);
}
};
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/// Calculates arithmetic mean of numbers.
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template <typename T, typename Data, typename Derived>
class AggregateFunctionAvgBase : public IAggregateFunctionDataHelper<Data, Derived>
{
public:
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using ResultType = std::conditional_t<IsDecimalNumber<T>, T, Float64>;
using ResultDataType = std::conditional_t<IsDecimalNumber<T>, DataTypeDecimal<T>, DataTypeNumber<Float64>>;
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using ColVecType = std::conditional_t<IsDecimalNumber<T>, ColumnDecimal<T>, ColumnVector<T>>;
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using ColVecResult = std::conditional_t<IsDecimalNumber<T>, ColumnDecimal<T>, ColumnVector<Float64>>;
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/// ctor for native types
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AggregateFunctionAvgBase(const DataTypes & argument_types_) : IAggregateFunctionDataHelper<Data, Derived>(argument_types_, {}), scale(0) {}
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/// ctor for Decimals
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AggregateFunctionAvgBase(const IDataType & data_type, const DataTypes & argument_types_)
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: IAggregateFunctionDataHelper<Data, Derived>(argument_types_, {}), scale(getDecimalScale(data_type))
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{
}
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DataTypePtr getReturnType() const override
{
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if constexpr (IsDecimalNumber<T>)
return std::make_shared<ResultDataType>(ResultDataType::maxPrecision(), scale);
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else
return std::make_shared<ResultDataType>();
}
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void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs, Arena *) const override
{
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this->data(place).numerator += this->data(rhs).numerator;
this->data(place).denominator += this->data(rhs).denominator;
}
void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
{
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writeBinary(this->data(place).numerator, buf);
writeVarUInt(this->data(place).denominator, buf);
}
void deserialize(AggregateDataPtr place, ReadBuffer & buf, Arena *) const override
{
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readBinary(this->data(place).numerator, buf);
readVarUInt(this->data(place).denominator, buf);
}
void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
{
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auto & column = static_cast<ColVecResult &>(to);
column.getData().push_back(this->data(place).template result<ResultType>());
}
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protected:
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UInt32 scale;
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};
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template <typename T, typename Data>
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class AggregateFunctionAvg final : public AggregateFunctionAvgBase<T, Data, AggregateFunctionAvg<T, Data>>
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{
public:
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using AggregateFunctionAvgBase<T, Data, AggregateFunctionAvg<T, Data>>::AggregateFunctionAvgBase;
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using ColVecType = std::conditional_t<IsDecimalNumber<T>, ColumnDecimal<T>, ColumnVector<T>>;
void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num, Arena *) const override
{
const auto & column = static_cast<const ColVecType &>(*columns[0]);
this->data(place).numerator += column.getData()[row_num];
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this->data(place).denominator += 1;
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}
String getName() const override { return "avg"; }
};
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}