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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-258) Use skip scan when SELECT DISTINCT on leading row key column(s)
Date Wed, 01 Jun 2016 22:49:59 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15311293#comment-15311293
] 

Lars Hofhansl commented on PHOENIX-258:
---------------------------------------

bq. For example, if we have a schema like VARCHAR, INT, INT, we need to pad for the 2nd and
3rd slot position

I think we only need to pad whatever the last distinct/groupby position is. So in the schema
above if the distinct is on key part1, we'd pad the VARCHAR, if the distinct is part1, part2,
we'd pad the INT if needed. (we wouldn't optimize this for distinct over all parts)
Pretty sure this works correctly in all cases now.



> 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-v10.txt, 258-v11.txt, 258-v12.txt,
258-v13.txt, 258-v14.txt, 258-v2.txt, 258-v3.txt, 258-v4.txt, 258-v5.txt, 258-v6.txt, 258-v7.txt,
258-v8.txt, 258-v9.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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