[GitHub] [spark] HeartSaVioR commented on pull request #35521: [SPARK-38212][SS] Remove out-of-watermark states for streaming dedup

[GitBox <gi...@apache.org>]

HeartSaVioR commented on pull request #35521:
URL: https://github.com/apache/spark/pull/35521#issuecomment-1039922686


   I agree about the problem description, but I'd like to see more thoughtful solution.
   
   Suppose we have perfect watermark with no delay allowance, and there is no event being out of order, then streaming dedup will do nothing on deduplication because effectively it will register the row in the state and evict it immediately.
   
   Personally, for this case, applying TTL against state row would be more sense to me. If we don't want to enforce watermark for the functionality, then we will end up with wall/processing time for TTL which may fall into indeterministic result, but setting TTL as huge interval like 2 hours would be acceptable tolerating such behavior. If we want to enforce watermark to let TTL work (TTL working with event time column), we may even produce deterministic result except late events.


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