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Posted to reviews@spark.apache.org by GitBox <gi...@apache.org> on 2020/07/07 08:39:26 UTC

[GitHub] [spark] cloud-fan commented on pull request #29021: [SPARK-32201][SQL] More general skew join pattern matching

cloud-fan commented on pull request #29021:
URL: https://github.com/apache/spark/pull/29021#issuecomment-654694004


   ```
   SMJ
        Sort
          Shuffle
        Sort
          HashAggregate
            Shuffle
   ```
   
   This is an interesting use case. We must be careful when dealing with it. The key of skew join handling is to split the skew partition into smaller parts. For `HashAggregate`, I'm not sure if this works, as now the values of the same key may exist in different after-split partitions. This makes `HashAggregate` incorrect.


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