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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-3550) Early skipping for limit operator at reduce stage
Date Mon, 08 Oct 2012 18:26:03 GMT

    [ https://issues.apache.org/jira/browse/HIVE-3550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13471726#comment-13471726
] 

Namit Jain commented on HIVE-3550:
----------------------------------

+1
                
> Early skipping for limit operator at reduce stage
> -------------------------------------------------
>
>                 Key: HIVE-3550
>                 URL: https://issues.apache.org/jira/browse/HIVE-3550
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Navis
>            Assignee: Navis
>            Priority: Trivial
>         Attachments: HIVE-3550.D5943.1.patch
>
>
> Queries with limit clause whose final result is from reduce stage could not be early
exited like map stage. But it seemed possible to just skip remaining lines. It can be accomplished
by adding just two lines. Is there any reason we should not to do that?
> {noformat}
> select key from src order by key limit 10;
> 1. current
> ExtractOperator: 3 forwarded 500 rows
> LimitOperator: 4 forwarded 10 rows
> 2. early skipping
> ExtractOperator: 3 forwarded 12 rows
> LimitOperator: 4 forwarded 10 rows
> {noformat}

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