ClickHouse/src/Functions/isNull.cpp
2021-08-09 18:01:08 +03:00

67 lines
2.0 KiB
C++

#include <Functions/IFunction.h>
#include <Functions/FunctionHelpers.h>
#include <Functions/FunctionFactory.h>
#include <DataTypes/DataTypesNumber.h>
#include <Core/ColumnNumbers.h>
#include <Columns/ColumnNullable.h>
namespace DB
{
namespace
{
/// Implements the function isNull which returns true if a value
/// is null, false otherwise.
class FunctionIsNull : public IFunction
{
public:
static constexpr auto name = "isNull";
static FunctionPtr create(ContextPtr)
{
return std::make_shared<FunctionIsNull>();
}
std::string getName() const override
{
return name;
}
size_t getNumberOfArguments() const override { return 1; }
bool useDefaultImplementationForNulls() const override { return false; }
bool useDefaultImplementationForConstants() const override { return true; }
bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
ColumnNumbers getArgumentsThatDontImplyNullableReturnType(size_t /*number_of_arguments*/) const override { return {0}; }
DataTypePtr getReturnTypeImpl(const DataTypes &) const override
{
return std::make_shared<DataTypeUInt8>();
}
ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t) const override
{
const ColumnWithTypeAndName & elem = arguments[0];
if (const auto * nullable = checkAndGetColumn<ColumnNullable>(*elem.column))
{
/// Merely return the embedded null map.
return nullable->getNullMapColumnPtr();
}
else
{
/// Since no element is nullable, return a zero-constant column representing
/// a zero-filled null map.
return DataTypeUInt8().createColumnConst(elem.column->size(), 0u);
}
}
};
}
void registerFunctionIsNull(FunctionFactory & factory)
{
factory.registerFunction<FunctionIsNull>(FunctionFactory::CaseInsensitive);
}
}