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https://issues.apache.org/jira/browse/DRILL-6755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16628170#comment-16628170
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ASF GitHub Bot commented on DRILL-6755:
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Ben-Zvi opened a new pull request #1480: DRILL-6755: Avoid building Hash Table
for inner/left join when probe side is empty
URL: https://github.com/apache/drill/pull/1480
This PR is split into two commits to help the reviewers:
(1) Preparations and cleanups: No change to the code's logic, only new
definitions and minor cleaning.
(2) The actual change: Define the flag `skipHashTableBuild` and use it to
skip initial hash-table setting, and later to kill the build side upstream and
skip the hash table build. (This also saves the useless work in the upstream;
e.g., more scanning).
Also included is a test of an inner join, with a NONE probe input, and
multiple input batches on the build side.
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> 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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