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

["Jesus Camacho Rodriguez (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-12492?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Work on HIVE-12492 started by Jesus Camacho Rodriguez.
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> 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: Jesus Camacho Rodriguez
>
> 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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