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https://issues.apache.org/jira/browse/IMPALA-6822?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tianyi Wang resolved IMPALA-6822.
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Resolution: Fixed
Fix Version/s: Impala 2.12.0
Impala 3.0
> Provide a query option to not shuffle on distinct exprs
> -------------------------------------------------------
>
> Key: IMPALA-6822
> URL: https://issues.apache.org/jira/browse/IMPALA-6822
> Project: IMPALA
> Issue Type: Improvement
> Components: Frontend
> Affects Versions: Impala 2.10.0, Impala 2.11.0, Impala 3.0, Impala 2.12.0,
> Impala 2.13.0
> Reporter: Tianyi Wang
> Assignee: Tianyi Wang
> Priority: Critical
> Labels: performance, planner, regression
> Fix For: Impala 3.0, Impala 2.12.0
>
>
> After IMPALA-4794, in a distinct aggregation, data will be shuffled on
> grouping exprs and distinct expr. It works well if the NDV of grouping exprs
> is low, but is an regression otherwise. We should provide a query operation
> to disable IMPALA-4794 and probably look to do smarter planning in the future.
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