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https://issues.apache.org/jira/browse/IMPALA-6867?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alex Rodoni closed IMPALA-6867.
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Resolution: Fixed
Fix Version/s: Impala 2.12.0
Impala 3.0
> Impala 2.12 & 3.0 Docs: Provide a query option to not shuffle on distinct
> exprs
> -------------------------------------------------------------------------------
>
> Key: IMPALA-6867
> URL: https://issues.apache.org/jira/browse/IMPALA-6867
> Project: IMPALA
> Issue Type: Sub-task
> Components: Docs
> Affects Versions: Impala 3.0, Impala 2.12.0
> Reporter: Alex Rodoni
> Assignee: Alex Rodoni
> Priority: Major
> Fix For: Impala 3.0, Impala 2.12.0
>
>
> https://gerrit.cloudera.org/#/c/9949/
> New query option:
> SHUFFLE_DISTINCT_EXPRS
> This options controls the shuffling behavior when a query has both grouping
> and distinct exprs. Impala can optionally include the distinct exprs in the
> hash exchange of the first aggregation phase to spread the data among more
> nodes. However, this plan requires another hash exchange on the grouping
> exprs in the second phase which is not required when omitting the distinct
> exprs in the first phase. Turning it off is recommended if the NDVs of the
> grouping exprs is high.
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