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https://issues.apache.org/jira/browse/HIVE-12492?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15300363#comment-15300363
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Jesus Camacho Rodriguez commented on HIVE-12492:
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Removing 2.1.0 target. Please feel free to commit to branch-2.1 anyway and fix
for 2.1.0 if this happens before the release.
> 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: Improvement
> Components: Query Planning
> Affects Versions: 1.3.0, 1.2.1, 2.0.0
> Reporter: Gopal V
> Assignee: Gopal V
>
> 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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