erichanwang opened a new pull request, #50839: URL: https://github.com/apache/arrow/pull/50839
### Rationale for this change The Union layout documentation does not explain that the type IDs stored in the types buffer can differ from the child array indices, or how the optional `typeIds` metadata maps children to physical type IDs. ### What changes are included in this PR? - Document the relationship between Union child array indices, physical type IDs, and the optional `typeIds` metadata. - Clarify that the types buffer stores the type ID for each slot. Fixes #22342. ### Are these changes tested? `git diff --check` passes and the RST change was reviewed against `Schema.fbs` and the existing Union layout documentation. A local Sphinx/RST checker is not installed in this environment. ### Are there any user-facing changes? No. * GitHub Issue: #22342 -- 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]
