[jira] [Commented] (DRILL-4415) Minimum parallelization width not respected in group scans

["Venki Korukanti (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-4415?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15163561#comment-15163561 ] 

Venki Korukanti commented on DRILL-4415:
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The issue here: GroupScan.enforceWidth is not overridden, UnionExchange is removed as part of the ExcessibleExchangeRemover. So there only one fragment which has GroupScan->Project->Screen. As the Screen has the max parallelization of 1, it overrides the GroupScan min parallelization. 

It seems GroupScan.enforceWidth API is unnecessary, instead ExcessibleExchangeRemover should look at GroupScan.minParallelization. Also in SimpleParallelizer we should through exceptions if encounter a situation where max parallelization of operator overrides min parallelization of another operator in the same fragment.

> Minimum parallelization width not respected in group scans
> ----------------------------------------------------------
>
>                 Key: DRILL-4415
>                 URL: https://issues.apache.org/jira/browse/DRILL-4415
>             Project: Apache Drill
>          Issue Type: Bug
>          Components:  Server
>            Reporter: MinJi Kim
>
> Even if the minimum parallelization widith is set to > 1 value, this value is not always respected.
> For example, in AggPruleBase, the decision to do two phase aggregation (create2PhasePlan) only takes into account the number of rows.  So, if table is small enough, even if the width is set to > 1 value, the plan will ignore the minimum width request. 



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