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https://issues.apache.org/jira/browse/PHOENIX-2965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15325639#comment-15325639
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Lars Hofhansl commented on PHOENIX-2965:
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It works fine with COUNT(DISTINCT pk1), COUNT(DISTINCT pk2), etc. so the 
replacement must do the right thing already.
Anyway... I am undoing this change until I can figure out how to do this. The 
interesting part is that we need the group by expressions to decide whether we 
can do the optimizations.


> Use DistinctPrefixFilter logic for COUNT(DISTINCT ...) and COUNT(...) GROUP BY
> ------------------------------------------------------------------------------
>
>                 Key: PHOENIX-2965
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-2965
>             Project: Phoenix
>          Issue Type: Sub-task
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 4.8.0
>
>         Attachments: 2965-v2.txt, 2965-v3.txt, 2965-v4.txt, 2965-v5.txt, 
> 2965-v6.txt, 2965.txt, PHOENIX-2965_wip.patch
>
>
> Parent uses skip scanning to optimize DISTINCT and certain GROUP BY 
> operations along the row key.
> COUNT queries are optimized differently, could be sped up significantly as 
> well.
> [~giacomotaylor], I might need to help into where COUNT(DISTINCT) queries are 
> planned and optimized.



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