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https://issues.apache.org/jira/browse/PHOENIX-258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15304850#comment-15304850
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Lars Hofhansl commented on PHOENIX-258:
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[~giacomotaylor] where/how is COUNT(DISTINCT ...) compiled?
I find that COUNT(DISTINCT...) does not benefit from this (takes minutes)
whereas SELECT COUNT(*) FROM (SELECT DISTINCT ...) does (takes a few ms).
Looks like COUNT(DISTINCT...) is compiled to a completely different plan.
> Use skip scan when SELECT DISTINCT on leading row key column(s)
> ---------------------------------------------------------------
>
> Key: PHOENIX-258
> URL: https://issues.apache.org/jira/browse/PHOENIX-258
> Project: Phoenix
> Issue Type: Task
> Reporter: ryang-sfdc
> Assignee: Lars Hofhansl
> Fix For: 4.8.0
>
> Attachments: 258-WIP.txt, 258-v1.txt, 258-v2.txt, 258-v3.txt,
> 258-v4.txt, 258-v5.txt, 258.txt, DistinctFixedPrefixFilter.java, in-clause.png
>
>
> create table(a varchar(32) not null, date date not null constraint pk primary
> key(a,date))
> [["PLAN"],["CLIENT PARALLEL 94-WAY FULL SCAN OVER foo"],[" SERVER
> AGGREGATE INTO ORDERED DISTINCT ROWS BY [a]"],["CLIENT MERGE SORT"]]
>
> We should skip scan.
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