ClickHouse/src/Functions/toNullable.cpp

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#include <Functions/IFunction.h>
#include <Functions/FunctionFactory.h>
#include <DataTypes/DataTypeNullable.h>
#include <Columns/ColumnNullable.h>
#include <Core/ColumnNumbers.h>
namespace DB
{
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namespace
{
/// If value is not Nullable or NULL, wraps it to Nullable.
class FunctionToNullable : public IFunction
{
public:
static constexpr auto name = "toNullable";
static FunctionPtr create(ContextPtr)
{
return std::make_shared<FunctionToNullable>();
}
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 & arguments) const override
{
return makeNullable(arguments[0]);
}
ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t) const override
{
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return makeNullable(arguments[0].column);
}
};
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}
void registerFunctionToNullable(FunctionFactory & factory)
{
factory.registerFunction<FunctionToNullable>();
}
}