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

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#pragma once
#include <DB/DataTypes/DataTypeAggregateFunction.h>
#include <DB/AggregateFunctions/IAggregateFunction.h>
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#include <DB/Columns/ColumnAggregateFunction.h>
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namespace DB
{
/** Не агрегатная функция, а адаптер агрегатных функций,
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* Агрегатные функции с суффиксом Merge принимают в качестве аргумента DataTypeAggregateFunction
* (состояние агрегатной функции, полученное ранее с помощью применения агрегатной функции с суффиксом State)
* и объединяют их при агрегации.
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*/
class AggregateFunctionMerge final : public IAggregateFunction
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{
private:
AggregateFunctionPtr nested_func_owner;
IAggregateFunction * nested_func;
public:
AggregateFunctionMerge(AggregateFunctionPtr nested_) : nested_func_owner(nested_), nested_func(nested_func_owner.get()) {}
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String getName() const override
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{
return nested_func->getName() + "Merge";
}
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DataTypePtr getReturnType() const override
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{
return nested_func->getReturnType();
}
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void setArguments(const DataTypes & arguments) override
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{
if (arguments.size() != 1)
throw Exception("Passed " + toString(arguments.size()) + " arguments to unary aggregate function " + this->getName(),
ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
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const DataTypeAggregateFunction * data_type = typeid_cast<const DataTypeAggregateFunction *>(&*arguments[0]);
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if (!data_type || data_type->getFunctionName() != nested_func->getName())
throw Exception("Illegal type " + arguments[0]->getName() + " of argument for aggregate function " + getName(),
ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
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nested_func->setArguments(data_type->getArgumentsDataTypes());
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}
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void setParameters(const Array & params) override
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{
nested_func->setParameters(params);
}
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void create(AggregateDataPtr place) const override
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{
nested_func->create(place);
}
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void destroy(AggregateDataPtr place) const noexcept override
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{
nested_func->destroy(place);
}
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bool hasTrivialDestructor() const override
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{
return nested_func->hasTrivialDestructor();
}
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size_t sizeOfData() const override
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{
return nested_func->sizeOfData();
}
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size_t alignOfData() const override
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{
return nested_func->alignOfData();
}
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void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const override
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{
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nested_func->merge(place, static_cast<const ColumnAggregateFunction &>(*columns[0]).getData()[row_num]);
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}
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void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const override
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{
nested_func->merge(place, rhs);
}
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void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
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{
nested_func->serialize(place, buf);
}
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void deserialize(AggregateDataPtr place, ReadBuffer & buf) const override
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{
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nested_func->deserialize(place, buf);
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}
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void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const override
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{
nested_func->insertResultInto(place, to);
}
static void addFree(const IAggregateFunction * that, AggregateDataPtr place, const IColumn ** columns, size_t row_num)
{
return static_cast<const AggregateFunctionMerge &>(*that).add(place, columns, row_num);
}
IAggregateFunction::AddFunc getAddressOfAddFunction() const override final { return &addFree; }
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};
}