gene-bordegaray commented on code in PR #24670:
URL: https://github.com/apache/datafusion/pull/24670#discussion_r3899536784
##########
datafusion/expr/src/expr_schema.rs:
##########
@@ -71,18 +71,23 @@ pub trait ExprSchemable {
-> Result<(DataType, bool)>;
}
-/// Derives the output field for a cast expression from the source field.
+/// Derives the output field for a cast expression from the source field, using
+/// explicit target metadata when supplied.
/// For `TryCast`, `force_nullable` is `true` since a failed cast returns NULL.
fn cast_output_field(
source_field: &FieldRef,
- target_type: &DataType,
+ target: &CastTarget,
force_nullable: bool,
) -> Arc<Field> {
+ let metadata = target
+ .metadata()
+ .cloned()
+ .unwrap_or_else(|| source_field.metadata().clone());
let mut f = source_field
.as_ref()
.clone()
- .with_data_type(target_type.clone())
- .with_metadata(source_field.metadata().clone());
+ .with_data_type(target.data_type().clone())
+ .with_metadata(metadata);
Review Comment:
yes sorry about the confusion I should've temporarily made this a draft, the
diff for this PR is much smaller. Allthat the `CastTarget` and protobuf changes
are mixed into this PR because I had stacked it on #24725 but they shouldn’t be
reviewed as part of the projection optimizer fix. I’m going to rebase this onto
#23169 after some discussion to go with that approach for the minor relese.
as far as this particular comment. I originally thought this too and
@gabotechs also asked about
[this](https://github.com/apache/datafusion/pull/24670#discussion_r3865163140),
its a subtle one. Let me know if that clarifies 👍
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