Panagiotis Garefalakis created HIVE-24308:
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Summary: FIX conditions used for DPHJ conversion
Key: HIVE-24308
URL: https://issues.apache.org/jira/browse/HIVE-24308
Project: Hive
Issue Type: Bug
Reporter: Panagiotis Garefalakis
Assignee: Panagiotis Garefalakis
Found a weird scenario when looking at the ConvertJoinMapJoin logic:
[https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/optimizer/ConvertJoinMapJoin.java#L1198]
When the distinct keys cannot fit in memory AND the DPHJ ShuffleSize is lower
than expected the code returns a MJ because of the condition above!
In general, I believe the ShuffleSize check:
[https://github.com/apache/hive/blob/052c9da958f5cf3998091a7eb4b24192a5bb61e9/ql/src/java/org/apache/hadoop/hive/ql/optimizer/ConvertJoinMapJoin.java#L1624]
should be part of the shuffleJoin DPHJ conversion.
And the preferred conversion would be: MJ > DPHJ > SMB
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