ClickHouse/dbms/src/Functions/finalizeAggregation.cpp

77 lines
2.2 KiB
C++

#include <Functions/IFunction.h>
#include <Functions/FunctionFactory.h>
#include <Functions/FunctionHelpers.h>
#include <DataTypes/DataTypeAggregateFunction.h>
#include <Columns/ColumnAggregateFunction.h>
#include <Common/typeid_cast.h>
namespace DB
{
namespace ErrorCodes
{
extern const int ILLEGAL_COLUMN;
extern const int ILLEGAL_TYPE_OF_ARGUMENT;
}
/** finalizeAggregation(agg_state) - get the result from the aggregation state.
* Takes state of aggregate function. Returns result of aggregation (finalized state).
*/
class FunctionFinalizeAggregation : public IFunction
{
public:
static constexpr auto name = "finalizeAggregation";
static FunctionPtr create(const Context &)
{
return std::make_shared<FunctionFinalizeAggregation>();
}
String getName() const override
{
return name;
}
bool isStateful() const override
{
return true;
}
size_t getNumberOfArguments() const override
{
return 1;
}
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
{
const DataTypeAggregateFunction * type = checkAndGetDataType<DataTypeAggregateFunction>(arguments[0].get());
if (!type)
throw Exception("Argument for function " + getName() + " must have type AggregateFunction - state of aggregate function.",
ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
return type->getReturnType();
}
void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t /*input_rows_count*/) override
{
const ColumnAggregateFunction * column_with_states
= typeid_cast<const ColumnAggregateFunction *>(&*block.getByPosition(arguments.at(0)).column);
if (!column_with_states)
throw Exception("Illegal column " + block.getByPosition(arguments.at(0)).column->getName()
+ " of first argument of function "
+ getName(),
ErrorCodes::ILLEGAL_COLUMN);
block.getByPosition(result).column = column_with_states->convertToValues();
}
};
void registerFunctionFinalizeAggregation(FunctionFactory & factory)
{
factory.registerFunction<FunctionFinalizeAggregation>();
}
}