dexterduck opened a new issue, #6886: URL: https://github.com/apache/arrow-datafusion/issues/6886
### Is your feature request related to a problem or challenge? I'm working on a project that requires using Arrow extension types. Because of the way extension types are encoded in `arrow-rs` (see apache/arrow-rs#4472) I have to keep track of type information at the field/schema level. This works at execution time, but I've run into an issue trying to extract metadata from a field during the planning phase as field metadata isn't being propagated. This seems to originate in the `ExprSchemable::to_field` trait, where when a field is constructed from an expression it only copies the datatype and nullability from the input schema. ### Describe the solution you'd like A reasonable approach to me would be to add a `metadata` method to the `ExprSchemable` trait that would forward field metadata for type-preserving expressions (e.g. column, alias, etc.) and return empty metadata for others. `ExprSchemable::to_field` could then be updated to pass the metadata to the `DFField` constructor. ### Describe alternatives you've considered The proposed solution would enable metadata propagation through expressions. I haven't gone through every logical plan node so it's possible I'm missing other places where metadata would be erased that would also need to be changed. ### Additional context _No response_ -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: github-unsubscr...@arrow.apache.org.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
