1 | #include <Functions/IFunctionImpl.h> |
---|---|
2 | #include <Functions/FunctionFactory.h> |
3 | #include <DataTypes/DataTypeLowCardinality.h> |
4 | #include <Columns/ColumnLowCardinality.h> |
5 | #include <Common/typeid_cast.h> |
6 | |
7 | |
8 | namespace DB |
9 | { |
10 | |
11 | namespace ErrorCodes |
12 | { |
13 | extern const int ILLEGAL_TYPE_OF_ARGUMENT; |
14 | } |
15 | |
16 | |
17 | class FunctionLowCardinalityKeys: public IFunction |
18 | { |
19 | public: |
20 | static constexpr auto name = "lowCardinalityKeys"; |
21 | static FunctionPtr create(const Context &) { return std::make_shared<FunctionLowCardinalityKeys>(); } |
22 | |
23 | String getName() const override { return name; } |
24 | |
25 | size_t getNumberOfArguments() const override { return 1; } |
26 | |
27 | bool useDefaultImplementationForNulls() const override { return false; } |
28 | bool useDefaultImplementationForConstants() const override { return true; } |
29 | bool useDefaultImplementationForLowCardinalityColumns() const override { return false; } |
30 | |
31 | DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override |
32 | { |
33 | auto * type = typeid_cast<const DataTypeLowCardinality *>(arguments[0].get()); |
34 | if (!type) |
35 | throw Exception("First first argument of function lowCardinalityKeys must be ColumnLowCardinality, but got" |
36 | + arguments[0]->getName(), ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT); |
37 | |
38 | return type->getDictionaryType(); |
39 | } |
40 | |
41 | void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t /*input_rows_count*/) override |
42 | { |
43 | auto arg_num = arguments[0]; |
44 | const auto & arg = block.getByPosition(arg_num); |
45 | auto & res = block.getByPosition(result); |
46 | const auto * low_cardinality_column = typeid_cast<const ColumnLowCardinality *>(arg.column.get()); |
47 | res.column = low_cardinality_column->getDictionary().getNestedColumn()->cloneResized(arg.column->size()); |
48 | } |
49 | }; |
50 | |
51 | |
52 | void registerFunctionLowCardinalityKeys(FunctionFactory & factory) |
53 | { |
54 | factory.registerFunction<FunctionLowCardinalityKeys>(); |
55 | } |
56 | |
57 | } |
58 |