LuciferYang opened a new issue, #10290: URL: https://github.com/apache/paimon/issues/10290
### Search before asking - [X] I searched in the [issues](https://github.com/apache/paimon/issues) and found no similar issues. ### Paimon version master (1.5-SNAPSHOT) ### Compute Engine Any engine issuing `ALTER TABLE` on a `MULTISET` column. ### Minimal reproduce step 1. Create a table with a `MULTISET` column, e.g. `tags MULTISET<INT>`. 2. Alter the multiset element type, e.g. to `MULTISET<BIGINT>` (or change the element nullability). ### What doesn't meet your expectations? The ALTER fails with a misleading `ColumnNotExistException`, even though the column exists. The nested type-update walk has no `MULTISET` case, so an off-by-one routes the change to `updateLastColumn` on an empty list. A `MULTISET<T>` is physically stored as `InternalMap<T, Int>`, so the element is a map key, and the read-side cast infrastructure has no MULTISET executor and deliberately forbids changing a map key type. So a multiset element type change cannot be applied to existing data and should be rejected at DDL with a clear, actionable message rather than a confusing "column not exist". ### Anything else? The `MULTISET` column's own top-level nullability change (the column, not its element) is a separate, supported operation and should keep working. ### Are you willing to submit a PR? - [X] I'm willing to submit a PR! -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
