1 | #include <Functions/IFunctionImpl.h> |
---|---|
2 | #include <Functions/FunctionFactory.h> |
3 | #include <Functions/FunctionHelpers.h> |
4 | #include <DataTypes/DataTypeString.h> |
5 | #include <Columns/ColumnString.h> |
6 | #include <Interpreters/Context.h> |
7 | #include <Common/Macros.h> |
8 | #include <Core/Field.h> |
9 | |
10 | |
11 | namespace DB |
12 | { |
13 | |
14 | namespace ErrorCodes |
15 | { |
16 | extern const int ILLEGAL_TYPE_OF_ARGUMENT; |
17 | extern const int ILLEGAL_COLUMN; |
18 | } |
19 | |
20 | /** Get scalar value of sub queries from query context via IAST::Hash. |
21 | */ |
22 | class FunctionGetScalar : public IFunction |
23 | { |
24 | public: |
25 | static constexpr auto name = "__getScalar"; |
26 | static FunctionPtr create(const Context & context) |
27 | { |
28 | return std::make_shared<FunctionGetScalar>(context); |
29 | } |
30 | |
31 | FunctionGetScalar(const Context & context_) : context(context_) {} |
32 | |
33 | String getName() const override |
34 | { |
35 | return name; |
36 | } |
37 | |
38 | size_t getNumberOfArguments() const override |
39 | { |
40 | return 1; |
41 | } |
42 | |
43 | DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override |
44 | { |
45 | if (arguments.size() != 1 || !isString(arguments[0].type) || !arguments[0].column || !isColumnConst(*arguments[0].column)) |
46 | throw Exception("Function "+ getName() + " accepts one const string argument", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT); |
47 | auto scalar_name = assert_cast<const ColumnConst &>(*arguments[0].column).getField().get<String>(); |
48 | scalar = context.getScalar(scalar_name).getByPosition(0); |
49 | return scalar.type; |
50 | } |
51 | |
52 | void executeImpl(Block & block, const ColumnNumbers &, size_t result, size_t input_rows_count) override |
53 | { |
54 | block.getByPosition(result).column = ColumnConst::create(scalar.column, input_rows_count); |
55 | } |
56 | |
57 | private: |
58 | mutable ColumnWithTypeAndName scalar; |
59 | const Context & context; |
60 | }; |
61 | |
62 | |
63 | void registerFunctionGetScalar(FunctionFactory & factory) |
64 | { |
65 | factory.registerFunction<FunctionGetScalar>(); |
66 | } |
67 | |
68 | } |
69 |