[jira] [Commented] (DRILL-6755) HashJoin should not build hash tables when probe side is empty.

["Boaz Ben-Zvi (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-6755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16626641#comment-16626641 ] 

Boaz Ben-Zvi commented on DRILL-6755:
-------------------------------------

More precisely, when the probe side does not even return a schema, just NONE.

When the probe side does first return a schema (i.e. OK_NEW_SCHEMA), then the Hash Tables are built, as the code does not "sniff" further into the probe side to check if actual data is coming.

 

 

> HashJoin should not build hash tables when probe side is empty.
> ---------------------------------------------------------------
>
>                 Key: DRILL-6755
>                 URL: https://issues.apache.org/jira/browse/DRILL-6755
>             Project: Apache Drill
>          Issue Type: Improvement
>            Reporter: Timothy Farkas
>            Assignee: Boaz Ben-Zvi
>            Priority: Major
>
> Currently when doing an Inner or a Right join we still build hashtables when the probe side is empty. A performance optimization would be to not build them.



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