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#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;
}
namespace
{
/** 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(ContextPtr)
{
return std::make_shared<FunctionFinalizeAggregation>();
}
String getName() const override
{
return name;
}
size_t getNumberOfArguments() const override
{
return 1;
}
bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return true; }
bool useDefaultImplementationForConstants() const override { return true; }
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
{
const DataTypeAggregateFunction * type = checkAndGetDataType<DataTypeAggregateFunction>(arguments[0].get());
if (!type)
{
throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
"Argument for function '{}' must have type AggregateFunction - state of aggregate function."
" Got '{}' instead", getName(), arguments[0]->getName());
}
return type->getReturnType();
}
ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
{
auto column = arguments.at(0).column;
if (!typeid_cast<const ColumnAggregateFunction *>(column.get()))
throw Exception(ErrorCodes::ILLEGAL_COLUMN, "Illegal column {} of first argument of function {}",
arguments.at(0).column->getName(), getName());
/// Column is copied here, because there is no guarantee that we own it.
auto mut_column = IColumn::mutate(std::move(column));
return ColumnAggregateFunction::convertToValues(std::move(mut_column));
}
};
}
REGISTER_FUNCTION(FinalizeAggregation)
{
factory.registerFunction<FunctionFinalizeAggregation>();
}
}
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