mesejo commented on code in PR #12308:
URL: https://github.com/apache/datafusion/pull/12308#discussion_r1742971283
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datafusion/functions/src/core/coalesce.rs:
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@@ -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:
Thanks for the review!
Wouldn't a coalesce be `non-null` (`is_nullable` -> false) if at least one
of the args is `non-null`? In other words, should the output of `is_nullable`
for `COALESCE(null, 5)` be false or true?
If I roll back this change, the test fails.
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