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Posted to issues@drill.apache.org by "Aman Sinha (JIRA)" <ji...@apache.org> on 2015/03/28 01:12:53 UTC

[jira] [Commented] (DRILL-1682) Avoid using UnionExchange for read workloads

    [ https://issues.apache.org/jira/browse/DRILL-1682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14384943#comment-14384943 ] 

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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