mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-18 04:12:19 +00:00
87 lines
2.8 KiB
C++
87 lines
2.8 KiB
C++
#include <Functions/IFunction.h>
|
|
#include <Functions/FunctionHelpers.h>
|
|
#include <Functions/FunctionFactory.h>
|
|
#include <DataTypes/DataTypesNumber.h>
|
|
#include <DataTypes/DataTypeNullable.h>
|
|
#include <Core/ColumnNumbers.h>
|
|
#include <Columns/ColumnNullable.h>
|
|
|
|
|
|
namespace DB
|
|
{
|
|
|
|
/// Implements the function nullIf which takes 2 arguments and returns
|
|
/// NULL if both arguments have the same value. Otherwise it returns the
|
|
/// value of the first argument.
|
|
class FunctionNullIf : public IFunction
|
|
{
|
|
private:
|
|
const Context & context;
|
|
public:
|
|
static constexpr auto name = "nullIf";
|
|
|
|
static FunctionPtr create(const Context & context)
|
|
{
|
|
return std::make_shared<FunctionNullIf>(context);
|
|
}
|
|
|
|
FunctionNullIf(const Context & context) : context(context) {}
|
|
|
|
std::string getName() const override
|
|
{
|
|
return name;
|
|
}
|
|
|
|
size_t getNumberOfArguments() const override { return 2; }
|
|
bool useDefaultImplementationForNulls() const override { return false; }
|
|
bool useDefaultImplementationForConstants() const override { return true; }
|
|
|
|
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
|
|
{
|
|
return makeNullable(arguments[0]);
|
|
}
|
|
|
|
void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) override
|
|
{
|
|
/// nullIf(col1, col2) == if(col1 == col2, NULL, col1)
|
|
|
|
Block temp_block = block;
|
|
|
|
size_t res_pos = temp_block.columns();
|
|
temp_block.insert({nullptr, std::make_shared<DataTypeUInt8>(), ""});
|
|
|
|
{
|
|
auto equals_func = FunctionFactory::instance().get("equals", context)->build(
|
|
{temp_block.getByPosition(arguments[0]), temp_block.getByPosition(arguments[1])});
|
|
equals_func->execute(temp_block, {arguments[0], arguments[1]}, res_pos, input_rows_count);
|
|
}
|
|
|
|
/// Argument corresponding to the NULL value.
|
|
size_t null_pos = temp_block.columns();
|
|
|
|
/// Append a NULL column.
|
|
ColumnWithTypeAndName null_elem;
|
|
null_elem.type = block.getByPosition(result).type;
|
|
null_elem.column = null_elem.type->createColumnConstWithDefaultValue(input_rows_count);
|
|
null_elem.name = "NULL";
|
|
|
|
temp_block.insert(null_elem);
|
|
|
|
auto func_if = FunctionFactory::instance().get("if", context)->build(
|
|
{temp_block.getByPosition(res_pos), temp_block.getByPosition(null_pos), temp_block.getByPosition(arguments[0])});
|
|
func_if->execute(temp_block, {res_pos, null_pos, arguments[0]}, result, input_rows_count);
|
|
|
|
block.getByPosition(result).column = std::move(temp_block.getByPosition(result).column);
|
|
}
|
|
};
|
|
|
|
|
|
|
|
void registerFunctionNullIf(FunctionFactory & factory)
|
|
{
|
|
factory.registerFunction<FunctionNullIf>(FunctionFactory::CaseInsensitive);
|
|
}
|
|
|
|
}
|
|
|