[jira] [Created] (FLINK-40368) Deduplicate output should only be insert-only when ordered by time attribute

["David Anderson (Jira)" <ji...@apache.org>]

David Anderson created FLINK-40368:
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             Summary: Deduplicate output should only be insert-only when ordered by time attribute
                 Key: FLINK-40368
                 URL: https://issues.apache.org/jira/browse/FLINK-40368
             Project: Flink
          Issue Type: Bug
          Components: Table SQL / Planner
    Affects Versions: 2.1.3, 2.2.1, 2.3.0
            Reporter: David Anderson


FLINK-37005 went too far, and the planner now incorrectly treats deduplication with ordering ASC on an ordering column that not a time attribute as producing an insert-only result. 

Claude suggests this approach for fixing this:

Make the inference guard match the translation guard — add the {{sortOnTimeAttributeOnly}} condition at FlinkChangelogModeInferenceProgram.scala:264 so non-time top-1 ranks fall into the existing {{ALL_CHANGES}} branch at line 286. One wrinkle: you can't simply call {{canConvertToDeduplicate}} there, because it calls {{{}ChangelogPlanUtils.inputInsertOnly{}}}, which reads a trait that isn't set yet during inference — the same trap documented at FlinkRelMdModifiedMonotonicity.scala:252. So expose {{RankUtil.sortOnTimeAttributeOnly}} (currently private) and combine it with the locally computed {{insertOnly}} from {{{}children{}}}.

Test gap worth closing at the same time: {{DeduplicateTest}} only covers {{proctime/rowtime/PROCTIME()}} ordering — there is no case with a plain column. Relatedly, {{StreamPhysicalRank.getDeduplicateDescription}} hardcodes {{{}order=[PROCTIME|ROWTIME]{}}}, which is another sign the dedup path assumes a time attribute throughout.



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