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https://issues.apache.org/jira/browse/DRILL-1682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14384943#comment-14384943
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Aman Sinha commented on DRILL-1682:
-----------------------------------
Need some clarity on this...why exactly should the UnionExchange be removed ?
Can we safely do that considering that row counts may be highly underestimated
? Seems like we should fix DRILL-1681 first.
> Avoid using UnionExchange for read workloads
> --------------------------------------------
>
> Key: DRILL-1682
> URL: https://issues.apache.org/jira/browse/DRILL-1682
> Project: Apache Drill
> Issue Type: Bug
> Components: Query Planning & Optimization
> Reporter: Hanifi Gunes
> Assignee: Aman Sinha
> Fix For: 0.9.0
>
>
> Use of UnionExchange in read workloads provides minor gains considering the
> implementation, maintenance overhead. Importantly it delays query termination
> as reported at DRILL-1681. Planner ideally should avoid using it for read
> queries.
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