pan3793 opened a new pull request, #52692:
URL: https://github.com/apache/spark/pull/52692

   Backport #44458 to branch-3.5.
   
   Justification: it fixes a hidden bug (until exposed by 
https://github.com/apache/spark/pull/44429) that has existed since 3.4.
   
   ### What changes were proposed in this pull request?
   
   In `V1Writes`, we try to avoid adding Sort if the output ordering always 
satisfies. However, the code is completely broken with two issues:
   - we put `SortOrder` as the child of another `SortOrder` and compare, which 
always returns false.
   - once we add a project to do `empty2null`, we change the query output 
attribute id and the sort order never matches.
   
   It's not a big issue as we still have QO rules to eliminate useless sorts, 
but https://github.com/apache/spark/pull/44429 exposes this problem because the 
way we optimize sort is a bit different. For `V1Writes`, we should always avoid 
adding sort even if the number of ordering key is less, to not change the user 
query.
   
   ### Why are the changes needed?
   
   fix code mistakes.
   
   ### Does this PR introduce _any_ user-facing change?
   
   no
   
   ### How was this patch tested?
   
   updated test
   
   ### Was this patch authored or co-authored using generative AI tooling?
   
   no
   
   


-- 
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]

Reply via email to