mesejo commented on code in PR #12308:
URL: https://github.com/apache/datafusion/pull/12308#discussion_r1743548464
##########
datafusion/functions/src/core/coalesce.rs:
##########
@@ -60,12 +60,16 @@ impl ScalarUDFImpl for CoalesceFunc {
}
fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
- Ok(arg_types[0].clone())
+ Ok(arg_types
+ .iter()
+ .find_or_first(|d| !d.is_null())
+ .unwrap()
+ .clone())
}
- // If all the element in coalesce is non-null, the result is non-null
+ // If all the elements in coalesce are non-null, the result is non-null
fn is_nullable(&self, args: &[Expr], schema: &dyn ExprSchema) -> bool {
- args.iter().any(|e| e.nullable(schema).ok().unwrap_or(true))
+ args.iter().all(|e| e.nullable(schema).ok().unwrap_or(true))
Review Comment:
Sorry, I was asking more about which function to use to coerce the types.
I see that in the `coerce_types` function, there is the following code:
```rust
if arg_types.is_empty() {
return exec_err!("coalesce must have at least one argument");
}
let new_type = type_union_resolution(arg_types)
.unwrap_or(arg_types.first().unwrap().clone());
```
Should I follow the same pattern?
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