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https://issues.apache.org/jira/browse/DRILL-6758?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16626222#comment-16626222
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Boaz Ben-Zvi commented on DRILL-6758:
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Yes; in this case the Hash-Join wastes time and memory by allocating vector
containers and copy each single value for these join keys. As a matter of fact,
in *every* join there is some waste (even when the join columns *are needed*
downstream) because +*both*+ columns are returned - but they are identical !!
> Hash Join should not return the join columns when they are not needed
> downstream
> --------------------------------------------------------------------------------
>
> Key: DRILL-6758
> URL: https://issues.apache.org/jira/browse/DRILL-6758
> Project: Apache Drill
> Issue Type: Improvement
> Components: Execution - Relational Operators, Query Planning &
> Optimization
> Affects Versions: 1.14.0
> Reporter: Boaz Ben-Zvi
> Assignee: Hanumath Rao Maduri
> Priority: Minor
> Fix For: 1.15.0
>
>
> Currently the Hash-Join operator returns all its (both sides) incoming
> columns. In cases where the join columns are not used further downstream,
> this is a waste (allocating vectors, copying each value, etc).
> Suggestion: Have the planner pass this information to the Hash-Join
> operator, to enable skipping the return of these columns.
>
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