1#include <Functions/IFunctionImpl.h>
2#include <Functions/FunctionHelpers.h>
3#include <Functions/FunctionFactory.h>
4#include <DataTypes/DataTypesNumber.h>
5#include <DataTypes/DataTypeNullable.h>
6#include <DataTypes/getLeastSupertype.h>
7#include <Core/ColumnNumbers.h>
8#include <Columns/ColumnNullable.h>
9
10
11namespace DB
12{
13
14/// Implements the function ifNull which takes 2 arguments and returns
15/// the value of the 1st argument if it is not null. Otherwise it returns
16/// the value of the 2nd argument.
17class FunctionIfNull : public IFunction
18{
19public:
20 static constexpr auto name = "ifNull";
21
22 FunctionIfNull(const Context & context_) : context(context_) {}
23
24 static FunctionPtr create(const Context & context)
25 {
26 return std::make_shared<FunctionIfNull>(context);
27 }
28
29 std::string getName() const override
30 {
31 return name;
32 }
33
34 size_t getNumberOfArguments() const override { return 2; }
35 bool useDefaultImplementationForNulls() const override { return false; }
36 bool useDefaultImplementationForConstants() const override { return true; }
37 ColumnNumbers getArgumentsThatDontImplyNullableReturnType(size_t /*number_of_arguments*/) const override { return {0}; }
38
39 DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
40 {
41 if (arguments[0]->onlyNull())
42 return arguments[1];
43
44 if (!arguments[0]->isNullable())
45 return arguments[0];
46
47 return getLeastSupertype({removeNullable(arguments[0]), arguments[1]});
48 }
49
50 void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) override
51 {
52 /// Always null.
53 if (block.getByPosition(arguments[0]).type->onlyNull())
54 {
55 block.getByPosition(result).column = block.getByPosition(arguments[1]).column;
56 return;
57 }
58
59 /// Could not contain nulls, so nullIf makes no sense.
60 if (!block.getByPosition(arguments[0]).type->isNullable())
61 {
62 block.getByPosition(result).column = block.getByPosition(arguments[0]).column;
63 return;
64 }
65
66 /// ifNull(col1, col2) == if(isNotNull(col1), assumeNotNull(col1), col2)
67
68 Block temp_block = block;
69
70 size_t is_not_null_pos = temp_block.columns();
71 temp_block.insert({nullptr, std::make_shared<DataTypeUInt8>(), ""});
72 size_t assume_not_null_pos = temp_block.columns();
73 temp_block.insert({nullptr, removeNullable(block.getByPosition(arguments[0]).type), ""});
74
75 auto is_not_null = FunctionFactory::instance().get("isNotNull", context)->build(
76 {temp_block.getByPosition(arguments[0])});
77
78 auto assume_not_null = FunctionFactory::instance().get("assumeNotNull", context)->build(
79 {temp_block.getByPosition(arguments[0])});
80
81 auto func_if = FunctionFactory::instance().get("if", context)->build(
82 {temp_block.getByPosition(is_not_null_pos), temp_block.getByPosition(assume_not_null_pos), temp_block.getByPosition(arguments[1])});
83
84 is_not_null->execute(temp_block, {arguments[0]}, is_not_null_pos, input_rows_count);
85 assume_not_null->execute(temp_block, {arguments[0]}, assume_not_null_pos, input_rows_count);
86 func_if->execute(temp_block, {is_not_null_pos, assume_not_null_pos, arguments[1]}, result, input_rows_count);
87
88 block.getByPosition(result).column = std::move(temp_block.getByPosition(result).column);
89 }
90
91private:
92 const Context & context;
93};
94
95
96void registerFunctionIfNull(FunctionFactory & factory)
97{
98 factory.registerFunction<FunctionIfNull>(FunctionFactory::CaseInsensitive);
99}
100
101}
102