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https://issues.apache.org/jira/browse/PHOENIX-2965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15326225#comment-15326225
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James Taylor commented on PHOENIX-2965:
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+1 for v11. One other related issue is with ORDER BY. It could also use
aggregate functions. For example:
{code}
SELECT COUNT(DISTINCT pk) FROM t ORDER BY COUNT(other_col);
{code}
Probably best to only use the optimization if statement.getOrderBy().isEmpty().
I filed PHOENIX-2989 with an idea on how we can use the optimization if HAVING
or ORDER BY only reference COUNT(DISTINCT) expressions.
> 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-v10.txt, 2965-v11.txt, 2965-v2.txt, 2965-v3.txt,
> 2965-v4.txt, 2965-v5.txt, 2965-v6.txt, 2965-v7.txt, 2965-v8.txt, 2965-v9.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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