Tianyi Wang created IMPALA-6822:

             Summary: 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
    Affects Versions: Impala 3.0, Impala 2.13.0
            Reporter: Tianyi Wang

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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