ClickHouse/dbms/src/Functions/isNull.cpp
Amos Bird 3cf2177268 Flexible fields assignment
Field f;

before:

f = Int64(-42);

after:

f = -42;
2018-10-24 08:47:33 +08:00

62 lines
1.7 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
{
/// 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(const Context &)
{
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; }
DataTypePtr getReturnTypeImpl(const DataTypes &) const override
{
return std::make_shared<DataTypeUInt8>();
}
void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t) override
{
const ColumnWithTypeAndName & elem = block.getByPosition(arguments[0]);
if (elem.column->isColumnNullable())
{
/// Merely return the embedded null map.
block.getByPosition(result).column = static_cast<const ColumnNullable &>(*elem.column).getNullMapColumnPtr();
}
else
{
/// Since no element is nullable, return a zero-constant column representing
/// a zero-filled null map.
block.getByPosition(result).column = DataTypeUInt8().createColumnConst(elem.column->size(), 0u);
}
}
};
void registerFunctionIsNull(FunctionFactory & factory)
{
factory.registerFunction<FunctionIsNull>();
}
}