ClickHouse/src/Functions/finalizeAggregation.cpp

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#include <Functions/IFunctionImpl.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;
}
bool useDefaultImplementationForConstants() const override { return true; }
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
{
const DataTypeAggregateFunction * type = checkAndGetDataType<DataTypeAggregateFunction>(arguments[0].get());
if (!type)
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{
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();
}
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t /*input_rows_count*/) const override
{
auto column = block.getByPosition(arguments.at(0)).column;
if (!typeid_cast<const ColumnAggregateFunction *>(column.get()))
throw Exception("Illegal column " + block.getByPosition(arguments.at(0)).column->getName()
+ " of first argument of function "
+ getName(),
ErrorCodes::ILLEGAL_COLUMN);
/// Column is copied here, because there is no guarantee that we own it.
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auto mut_column = IColumn::mutate(std::move(column));
block.getByPosition(result).column = ColumnAggregateFunction::convertToValues(std::move(mut_column));
}
};
void registerFunctionFinalizeAggregation(FunctionFactory & factory)
{
factory.registerFunction<FunctionFinalizeAggregation>();
}
}