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Posted to issues@tajo.apache.org by "Jihoon Son (JIRA)" <ji...@apache.org> on 2015/08/25 11:24:49 UTC

[jira] [Resolved] (TAJO-1766) Improve the performance of cross join

     [ https://issues.apache.org/jira/browse/TAJO-1766?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jihoon Son resolved TAJO-1766.
------------------------------
    Resolution: Fixed

Committed to master and 0.11.0

> Improve the performance of cross join
> -------------------------------------
>
>                 Key: TAJO-1766
>                 URL: https://issues.apache.org/jira/browse/TAJO-1766
>             Project: Tajo
>          Issue Type: Improvement
>          Components: distributed query plan
>            Reporter: Jihoon Son
>            Assignee: Jihoon Son
>             Fix For: 0.11.0
>
>
> Cross join is one of the very heavy operations. Furthermore, this operator is performed by a single worker in the current implementation. (Please see the implementation of HashPartitioner. If partitionKeyIds is empty, getPartition() always returns a single value.)
> One possible alternative is executing cross join with broadcast join. That is, outer table (smaller one) is always broadcasted, and join is performed by the machine who stores a part of inner table.
> To do so, a new session variable is required to set the broadcast threshold for cross join. 



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