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Posted to dev@hive.apache.org by "Gopal V (JIRA)" <ji...@apache.org> on 2015/11/22 14:28:10 UTC

[jira] [Created] (HIVE-12492) MapJoin: 4 million unique integers seems to be a probe plateau

Gopal V created HIVE-12492:
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             Summary: MapJoin: 4 million unique integers seems to be a probe plateau
                 Key: HIVE-12492
                 URL: https://issues.apache.org/jira/browse/HIVE-12492
             Project: Hive
          Issue Type: Bug
            Reporter: Gopal V
            Assignee: Gopal V
             Fix For: 2.0.0


After 4 million keys, the map-join implementation seems to suffer from a performance degradation. 

The hashtable build & probe time makes this very inefficient, even if the data is very compact (i.e 2 ints).

Falling back onto the shuffle join or bucket map-join is useful after 2^22 items.



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