Trikooo opened a new issue, #20290:
URL: https://github.com/apache/datafusion/issues/20290
### Is your feature request related to a problem or challenge?
Related to #20012
Currently, the return field of `ScalarFunction`s is being computed three
times during the query's lifecycle, during which the query's expression might
change.
for example when a udf needs to implicitly cast a literal, it wraps that
literal in a cast and recomputes the return field again after initial
computation without the cast, leading to inconsistent results.
### Describe the solution you'd like
Calculate the `return_type` during creation.
```rust
#[derive(Clone, PartialEq, Eq, PartialOrd, Hash, Debug)]
pub struct ScalarFunction {
/// The function
pub func: Arc<crate::ScalarUDF>,
/// List of expressions to feed to the functions as arguments
pub args: Vec<Expr>,
/// Return field of the function
return_field: FieldRef,
}
```
Not sure if a new constructor `ScalarFunction::new_udf_with_return_field`
should be created or change the original `ScalarFunction::new_udf`
### Describe alternatives you've considered
_No response_
### Additional context
#13825 proposed a similar approach.
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