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