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#include <Functions/IFunction.h>
#include <Functions/FunctionFactory.h>
#include <DataTypes/DataTypeLowCardinality.h>
#include <Columns/ColumnLowCardinality.h>
#include <Common/typeid_cast.h>
namespace DB
{
namespace ErrorCodes
{
extern const int ILLEGAL_TYPE_OF_ARGUMENT;
}
namespace
{
class FunctionLowCardinalityKeys: public IFunction
{
public:
static constexpr auto name = "lowCardinalityKeys";
static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionLowCardinalityKeys>(); }
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; }
bool useDefaultImplementationForLowCardinalityColumns() const override { return false; }
bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
{
const auto * type = typeid_cast<const DataTypeLowCardinality *>(arguments[0].get());
if (!type)
throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
"First first argument of function lowCardinalityKeys must be ColumnLowCardinality, "
"but got {}", arguments[0]->getName());
return type->getDictionaryType();
}
ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
{
const auto & arg = arguments[0];
const auto * low_cardinality_column = typeid_cast<const ColumnLowCardinality *>(arg.column.get());
return low_cardinality_column->getDictionary().getNestedColumn()->cloneResized(arg.column->size());
}
};
}
REGISTER_FUNCTION(LowCardinalityKeys)
{
factory.registerFunction<FunctionLowCardinalityKeys>();
}
}
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