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From "Daniel Dai (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PIG-3557) Implement optimizations for LIMIT
Date Tue, 14 Jan 2014 21:11:20 GMT

    [ https://issues.apache.org/jira/browse/PIG-3557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13871183#comment-13871183
] 

Daniel Dai commented on PIG-3557:
---------------------------------

1. You can check requestedParallelism for the tezOperator. This should be doable.

2. We can do a non-sorted scatter-gather, but this depends on TEZ-661, we cannot proceed now

4. We could use combiner and duplicate POLimit in the combiner. Otherwise, plan looks good.

> Implement optimizations for LIMIT
> ---------------------------------
>
>                 Key: PIG-3557
>                 URL: https://issues.apache.org/jira/browse/PIG-3557
>             Project: Pig
>          Issue Type: Sub-task
>          Components: tez
>    Affects Versions: tez-branch
>            Reporter: Alex Bain
>            Assignee: Alex Bain
>
> Implement optimizations for LIMIT when other parts of Pig-on-Tez are more mature. Some
of the optimizations mentioned by Daniel include:
> 1. If the previous stage using 1 reduce, no need to add one more vertex
> 2. If the limitplan is null (ie, not the "limited order by" case), we might not need
a shuffle edge, a pass through edge should be enough if possible
> 3. Similar to PIG-1270, we can push limit to InputHandler
> 4. We also need to think through the "limited order by" case once "order by" is implemented



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