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

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#pragma once
#include <DB/DataTypes/DataTypeAggregateFunction.h>
#include <DB/AggregateFunctions/IAggregateFunction.h>
namespace DB
{
/** Не агрегатная функция, а адаптер агрегатных функций,
* 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.
*/
class AggregateFunctionMerge final : public IAggregateFunction
{
private:
AggregateFunctionPtr nested_func_owner;
IAggregateFunction * nested_func;
public:
AggregateFunctionMerge(AggregateFunctionPtr nested_) : nested_func_owner(nested_), nested_func(nested_func_owner.get()) {}
String getName() const
{
return nested_func->getName() + "Merge";
}
DataTypePtr getReturnType() const
{
return nested_func->getReturnType();
}
void setArguments(const DataTypes & arguments)
{
if (arguments.size() != 1)
throw Exception("Passed " + toString(arguments.size()) + " arguments to unary aggregate function " + this->getName(),
ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
const DataTypeAggregateFunction * data_type = typeid_cast<const DataTypeAggregateFunction *>(&*arguments[0]);
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);
nested_func->setArguments(data_type->getArgumentsDataTypes());
}
void setParameters(const Array & params)
{
nested_func->setParameters(params);
}
void create(AggregateDataPtr place) const
{
nested_func->create(place);
}
void destroy(AggregateDataPtr place) const noexcept
{
nested_func->destroy(place);
}
bool hasTrivialDestructor() const
{
return nested_func->hasTrivialDestructor();
}
size_t sizeOfData() const
{
return nested_func->sizeOfData();
}
size_t alignOfData() const
{
return nested_func->alignOfData();
}
void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num) const
{
nested_func->merge(place, static_cast<const ColumnAggregateFunction &>(*columns[0]).getData()[row_num]);
}
void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
{
nested_func->merge(place, rhs);
}
void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
{
nested_func->serialize(place, buf);
}
void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
{
nested_func->deserializeMerge(place, buf);
}
void insertResultInto(ConstAggregateDataPtr place, IColumn & to) const
{
nested_func->insertResultInto(place, to);
}
};
}