findepi commented on code in PR #17521:
URL: https://github.com/apache/datafusion/pull/17521#discussion_r2341196453
##########
datafusion/optimizer/src/simplify_expressions/simplify_predicates.rs:
##########
@@ -204,7 +204,13 @@ fn find_most_restrictive_predicate(
if let Some(scalar) = scalar_value {
if let Some(current_best) = best_value {
- let comparison = scalar.try_cmp(current_best)?;
+ // Only compare if the scalar values have compatible types
+ // If they don't have compatible types, we can't determine
which is more restrictive
+ let Ok(comparison) = scalar.try_cmp(current_best) else {
+ // Can't compare - types are incompatible, so we can't
simplify
Review Comment:
good idea, please do
this function is used inside `fn simplify_column_predicates(predicates:
Vec<Expr>) -> Result<Vec<Expr>>`
returning `Ok(None)` is always _correct_ from correctness perspective. i.e.
we won't simplify something that we could simplify. this also leads as to a
test we could add
```
SELECT ... FROM ... WHERE a < 5 AND CAST(a AS varchar) < 'abc' AND a < 6
```
this should be simplified to `a < 5 AND CAST(a AS varchar)`. I.e. the `a ?
const` comparisons can be simplified using `find_most_restrictive_predicate`.
The `f(a) ? const` comparisons cannot.
current code in main fails (bad)
current code in PR does not fail (better), but the root cause (comparing
unrelated values) is not fixed (bad)
probably a better fix would be to delete the line here
https://github.com/apache/datafusion/blob/77ee675d70545b709b2a13f76c939c519c18493e/datafusion/optimizer/src/simplify_expressions/simplify_predicates.rs#L248-L249
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