ClickHouse/dbms/src/Functions/ifNull.cpp

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#include <Functions/IFunction.h>
#include <Functions/FunctionHelpers.h>
#include <Functions/FunctionFactory.h>
#include <DataTypes/DataTypesNumber.h>
#include <DataTypes/DataTypeNullable.h>
#include <DataTypes/getLeastSupertype.h>
#include <Core/ColumnNumbers.h>
#include <Columns/ColumnNullable.h>
namespace DB
{
/// Implements the function ifNull which takes 2 arguments and returns
/// the value of the 1st argument if it is not null. Otherwise it returns
/// the value of the 2nd argument.
class FunctionIfNull : public IFunction
{
public:
static constexpr auto name = "ifNull";
FunctionIfNull(const Context & context) : context(context) {}
static FunctionPtr create(const Context & context)
{
return std::make_shared<FunctionIfNull>(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
{
if (arguments[0]->onlyNull())
return arguments[1];
if (!arguments[0]->isNullable())
return arguments[0];
return getLeastSupertype({removeNullable(arguments[0]), arguments[1]});
}
void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) override
{
/// Always null.
if (block.getByPosition(arguments[0]).type->onlyNull())
{
block.getByPosition(result).column = block.getByPosition(arguments[1]).column;
return;
}
/// Could not contain nulls, so nullIf makes no sense.
if (!block.getByPosition(arguments[0]).type->isNullable())
{
block.getByPosition(result).column = block.getByPosition(arguments[0]).column;
return;
}
/// ifNull(col1, col2) == if(isNotNull(col1), assumeNotNull(col1), col2)
Block temp_block = block;
size_t is_not_null_pos = temp_block.columns();
temp_block.insert({nullptr, std::make_shared<DataTypeUInt8>(), ""});
size_t assume_not_null_pos = temp_block.columns();
temp_block.insert({nullptr, removeNullable(block.getByPosition(arguments[0]).type), ""});
auto is_not_null = FunctionFactory::instance().get("isNotNull", context)->build(
{temp_block.getByPosition(arguments[0])});
auto assume_not_null = FunctionFactory::instance().get("assumeNotNull", context)->build(
{temp_block.getByPosition(arguments[0])});
auto func_if = FunctionFactory::instance().get("if", context)->build(
{temp_block.getByPosition(is_not_null_pos), temp_block.getByPosition(assume_not_null_pos), temp_block.getByPosition(arguments[1])});
is_not_null->execute(temp_block, {arguments[0]}, is_not_null_pos, input_rows_count);
assume_not_null->execute(temp_block, {arguments[0]}, assume_not_null_pos, input_rows_count);
func_if->execute(temp_block, {is_not_null_pos, assume_not_null_pos, arguments[1]}, result, input_rows_count);
block.getByPosition(result).column = std::move(temp_block.getByPosition(result).column);
}
private:
const Context & context;
};
void registerFunctionIfNull(FunctionFactory & factory)
{
factory.registerFunction<FunctionIfNull>(FunctionFactory::CaseInsensitive);
}
}