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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-3562) Some limit can be pushed down to map stage
Date Sat, 24 Aug 2013 04:21:52 GMT

    [ https://issues.apache.org/jira/browse/HIVE-3562?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13749296#comment-13749296
] 

Ashutosh Chauhan commented on HIVE-3562:
----------------------------------------

I agree that will be quite a bit of work and given that this patch is out there for long,
We should try to get this in without major rework. Though, I think hash for FS will make this
optimization with HIVE-4002 real cool.  
                
> Some limit can be pushed down to map stage
> ------------------------------------------
>
>                 Key: HIVE-3562
>                 URL: https://issues.apache.org/jira/browse/HIVE-3562
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Navis
>            Assignee: Navis
>            Priority: Trivial
>         Attachments: HIVE-3562.D5967.1.patch, HIVE-3562.D5967.2.patch, HIVE-3562.D5967.3.patch,
HIVE-3562.D5967.4.patch, HIVE-3562.D5967.5.patch, HIVE-3562.D5967.6.patch
>
>
> Queries with limit clause (with reasonable number), for example
> {noformat}
> select * from src order by key limit 10;
> {noformat}
> makes operator tree, 
> TS-SEL-RS-EXT-LIMIT-FS
> But LIMIT can be partially calculated in RS, reducing size of shuffling.
> TS-SEL-RS(TOP-N)-EXT-LIMIT-FS

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