1#include <Functions/IFunctionImpl.h>
2#include <Functions/FunctionFactory.h>
3#include <DataTypes/DataTypesNumber.h>
4#include <Columns/ColumnsNumber.h>
5
6
7namespace DB
8{
9
10/** ignoreExceptNull(...) is a function that takes any arguments, and always returns 0 except Null.
11 */
12 class FunctionIgnoreExceptNull : public IFunction
13 {
14 public:
15 static constexpr auto name = "ignoreExceptNull";
16 static FunctionPtr create(const Context &)
17 {
18 return std::make_shared<FunctionIgnoreExceptNull>();
19 }
20
21 bool isVariadic() const override
22 {
23 return true;
24 }
25 size_t getNumberOfArguments() const override
26 {
27 return 0;
28 }
29
30 String getName() const override
31 {
32 return name;
33 }
34
35 DataTypePtr getReturnTypeImpl(const DataTypes & /*arguments*/) const override
36 {
37 return std::make_shared<DataTypeUInt8>();
38 }
39
40 void executeImpl(Block & block, const ColumnNumbers &, size_t result, size_t input_rows_count) override
41 {
42 /// This function is mainly used in query analysis instead of "in" functions
43 /// in the case when only header is needed and set for in is not calculated.
44 /// Because of that function must return the same column type as "in" function, which is ColumnUInt8.
45 auto res = ColumnUInt8::create(input_rows_count, 0);
46 block.getByPosition(result).column = std::move(res);
47 }
48 };
49
50
51 void registerFunctionIgnoreExceptNull(FunctionFactory & factory)
52 {
53 factory.registerFunction<FunctionIgnoreExceptNull>();
54 }
55
56}
57