cloud-fan opened a new pull request, #57375: URL: https://github.com/apache/spark/pull/57375
### What changes were proposed in this pull request? Followup to https://github.com/apache/spark/pull/57177. This change makes `CombineInternal` serialize and deserialize the placeholder buffer created for an empty partition. It encodes a missing item type as a zero-length type section and uses a default string serde for the necessarily empty sketch. ### Why are the changes needed? An untouched `approx_top_k_combine` buffer has no item type. It can nevertheless be serialized between aggregation stages, where selecting a type-specific serde or serializing the type currently throws. Preserving the empty placeholder allows the later merge to initialize it from real input. ### Does this PR introduce _any_ user-facing change? Yes. `approx_top_k_combine` no longer fails when an empty partition contributes an untouched placeholder buffer between aggregation stages. ### How was this patch tested? Added a regression test to `ApproxTopKSuite` that round-trips an empty combine buffer and verifies that its missing item type, sketch, and configured size are preserved. The staged workflow will run the required fail-before and pass-after suite cycle before opening the pull request. ### Was this patch authored or co-authored using generative AI tooling? Generated-by: Codex (GPT-5) -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
