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

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#pragma once
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#include <DB/IO/WriteHelpers.h>
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#include <DB/AggregateFunctions/IAggregateFunction.h>
namespace DB
{
/** Интерфейс для агрегатных функций, принимающих одно значение. Это почти все агрегатные функции.
*/
template <typename T, typename Derived>
class IUnaryAggregateFunction : public IAggregateFunctionHelper<T>
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{
private:
Derived & getDerived() { return static_cast<Derived &>(*this); }
const Derived & getDerived() const { return static_cast<const Derived &>(*this); }
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public:
void setArguments(const DataTypes & arguments) override final
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{
if (arguments.size() != 1)
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throw Exception("Passed " + toString(arguments.size()) + " arguments to unary aggregate function " + this->getName(),
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ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
getDerived().setArgument(arguments[0]);
}
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/// Добавить значение.
void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override final
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{
getDerived().addImpl(place, *columns[0], row_num);
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}
static void addFree(const IAggregateFunction * that, AggregateDataPtr place, const IColumn ** columns, size_t row_num)
{
return static_cast<const Derived &>(*that).addImpl(place, *columns[0], row_num);
}
IAggregateFunction::AddFunc getAddressOfAddFunction() const override { return &addFree; }
/** Реализуйте это в классе-наследнике:
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* void addImpl(AggregateDataPtr place, const IColumn & column, size_t row_num) const;
* void setArgument(const DataTypePtr & argument);
*/
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};
}