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From "Samarth Jain (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-3773) Implement FIRST_VALUES aggregate function
Date Wed, 31 May 2017 05:25:04 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-3773?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16030654#comment-16030654
] 

Samarth Jain commented on PHOENIX-3773:
---------------------------------------

[~singamteja] - the patch name should have PHOENIX-3773 and not PHOENIX-3733. Also, if you
are generating a patch using the 4.x-HBase-0.98 branch, then you should end it with _4.x-HBase-0.98
to tell the QA bot to apply the patch to that branch. It is possible that a patch for 4.x-HBase-0.98
branch may not apply directly to master or vice-versa.

> Implement FIRST_VALUES aggregate function
> -----------------------------------------
>
>                 Key: PHOENIX-3773
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-3773
>             Project: Phoenix
>          Issue Type: New Feature
>            Reporter: James Taylor
>            Assignee: Loknath Priyatham Teja Singamsetty 
>              Labels: SFDC
>             Fix For: 4.11.0
>
>         Attachments: PHOENIX-3733.v4.patch, PHOENIX-3773.patch, PHOENIX-3773.v2.patch,
PHOENIX-3773.v3.patch
>
>
> Similar to FIRST_VALUE, but would allow the user to specify how many values to keep.
This could use a MinMaxPriorityQueue under the covers and be much more efficient than using
multiple NTH_VALUE calls to do the same like this:
> {code}
> SELECT entity_id,
>        NTH_VALUE(user_id,1) WITHIN GROUP (ORDER BY last_read_date DESC) as nth1_user_id,
>        NTH_VALUE(user_id,2) WITHIN GROUP (ORDER BY last_read_date DESC) as nth2_user_id,
>        NTH_VALUE(user_id,3) WITHIN GROUP (ORDER BY last_read_date DESC) as nth3_user_id,
>        count(*)
> FROM  MY_TABLE 
> WHERE tenant_id='00Dx0000000XXXX'
> AND entity_id in ('0D5x000000ABCD','0D5x000000ABCE')
> GROUP BY entity_id;
> {code}



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