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https://issues.apache.org/jira/browse/PHOENIX-2965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15321329#comment-15321329
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Lars Hofhansl commented on PHOENIX-2965:
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* {{SELECT COUNT(DISTINCT pk1), COUNT(DISTINCT pk2) FROM t}} will use the
optimization, but {{SELECT COUNT(DISTINCT pk2), COUNT(DISTINCT pk3) FROM t}}
will not (since it cannot use a prefix for the skipcanning.
* {{COUNT(DISTINCT pk1), COUNT(DISTINCT pk2)}} will skip scan along pk1, pk2,
and since filtering is done first in the FilterList it will work correctly.
> 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
> Fix For: 4.8.0
>
> Attachments: 2965-v2.txt, 2965-v3.txt, 2965.txt
>
>
> 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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