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https://issues.apache.org/jira/browse/DRILL-4415?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15163561#comment-15163561
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Venki Korukanti edited comment on DRILL-4415 at 2/24/16 7:29 PM:
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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 throw exceptions if encounter a situation where
max parallelization of operator overrides min parallelization of another
operator in the same fragment.
was (Author: vkorukanti):
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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