#include <Functions/IFunction.h>
#include <Functions/FunctionFactory.h>


namespace DB
{
namespace
{

class FunctionIdentity : public IFunction
{
public:
    static constexpr auto name = "identity";
    static FunctionPtr create(ContextPtr)
    {
        return std::make_shared<FunctionIdentity>();
    }

    String getName() const override { return name; }
    size_t getNumberOfArguments() const override { return 1; }
    bool isSuitableForConstantFolding() const override { return false; }
    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }

    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        return arguments.front();
    }

    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
    {
        return arguments.front().column;
    }
};

}

REGISTER_FUNCTION(Identity)
{
    factory.registerFunction<FunctionIdentity>();
}

}