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

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#pragma once
#include <DB/AggregateFunctions/AggregateFunctionsMinMaxAny.h>
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#include <DB/AggregateFunctions/IBinaryAggregateFunction.h>
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namespace DB
{
/// Возможные значения параметров шаблонов см. в AggregateFunctionsMinMaxAny.h
template <typename ResultData, typename ValueData>
struct AggregateFunctionsArgMinMaxData
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{
using ResultData_t = ResultData;
using ValueData_t = ValueData;
ResultData result; // аргумент, при котором достигается минимальное/максимальное значение value.
ValueData value; // значение, для которого считается минимум/максимум.
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};
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/// Возвращает первое попавшееся значение arg для минимального/максимального value. Пример: argMax(arg, value).
template <typename Data>
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class AggregateFunctionsArgMinMax final : public IBinaryAggregateFunction<Data, AggregateFunctionsArgMinMax<Data>>
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{
private:
DataTypePtr type_res;
DataTypePtr type_val;
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public:
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String getName() const override { return (0 == strcmp(Data::ValueData_t::name(), "min")) ? "argMin" : "argMax"; }
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DataTypePtr getReturnType() const override
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{
return type_res;
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}
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void setArgumentsImpl(const DataTypes & arguments)
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{
type_res = arguments[0];
type_val = arguments[1];
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}
void addImpl(AggregateDataPtr place, const IColumn & column_arg, const IColumn & column_max, size_t row_num, Arena *) const
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{
if (this->data(place).value.changeIfBetter(column_max, row_num))
this->data(place).result.change(column_arg, row_num);
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}
void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs, Arena * arena) const override
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{
if (this->data(place).value.changeIfBetter(this->data(rhs).value))
this->data(place).result.change(this->data(rhs).result);
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}
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void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
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{
this->data(place).result.write(buf, *type_res.get());
this->data(place).value.write(buf, *type_val.get());
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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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this->data(place).result.read(buf, *type_res.get());
this->data(place).value.read(buf, *type_val.get());
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}
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void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
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{
this->data(place).result.insertResultInto(to);
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}
};
}