nagisa-kunhah commented on code in PR #59130:
URL: https://github.com/apache/doris/pull/59130#discussion_r2648928886
##########
be/src/vec/functions/function_map.cpp:
##########
@@ -792,6 +793,74 @@ class FunctionDeduplicateMap : public IFunction {
private:
};
+class FunctionMapConcat : public IFunction {
+public:
+ static constexpr auto name = "map_concat";
+ static FunctionPtr create() { return
std::make_shared<FunctionMapConcat>(); }
+ String get_name() const override { return name; }
+ bool is_variadic() const override { return true; }
+ size_t get_number_of_arguments() const override { return 0; }
+ DataTypePtr get_return_type_impl(const DataTypes& arguments) const
override {
+ DCHECK(arguments.size() > 0)
+ << "function: " << get_name() << ", arguments should not be
empty";
+ return arguments[0];
Review Comment:
Thank you for the review!
Yes, the return type is consistent with the FE logic. The BE receives
pre-processed types from FE, and all argument types are already unified at this
point.
For example, when running the SQL:
`select map_concat(map(1,2), map('3','4'));`
I verified this with GDB debugging at `function_map.cpp:806`. The results
show that FE has already performed type casting:
```
// arguments[0]: map(1,2) key type
(gdb) p
*(((DataTypeNullable*)((DataTypeMap*)arguments[0].get())->key_type.get())->nested_data_type.get())
$14 = (DataTypeString) { ... static PType = TYPE_STRING, _primitive_type =
TYPE_STRING }
// arguments[0]: map(1,2) value type
(gdb) p
*(((DataTypeNullable*)((DataTypeMap*)arguments[0].get())->value_type.get())->nested_data_type.get())
$15 = (DataTypeString) { ... static PType = TYPE_STRING, _primitive_type =
TYPE_STRING }
// arguments[1]: map('3','4') key type
(gdb) p
*(((DataTypeNullable*)((DataTypeMap*)arguments[1].get())->key_type.get())->nested_data_type.get())
$16 = (DataTypeString) { ... static PType = TYPE_STRING, _primitive_type =
TYPE_STRING }
// arguments[1]: map('3','4') value type
(gdb) p
*(((DataTypeNullable*)((DataTypeMap*)arguments[1].get())->value_type.get())->nested_data_type.get())
$17 = (DataTypeString) { ... static PType = TYPE_STRING, _primitive_type =
TYPE_STRING }
```
As you can see, both `map(1,2)` and `map('3','4')` have been converted to
`Map<String, String>` by FE before reaching BE. Therefore, returning
arguments[0] is safe and matches FE's type inference logic.
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