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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-14002) Extend limit propagation to subsequent RS operators
Date Tue, 14 Jun 2016 22:56:30 GMT

    [ https://issues.apache.org/jira/browse/HIVE-14002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15330819#comment-15330819
] 

Ashutosh Chauhan commented on HIVE-14002:
-----------------------------------------

I am not sure if we can allow *any* operators between two RSs other than GBy. e.g., filter
can be problematic if first Limit only generates N rows which filters eat all of it. We will
get incorrect result. Even for Select operator we can allow this only for column references
and constants.

> Extend limit propagation to subsequent RS operators
> ---------------------------------------------------
>
>                 Key: HIVE-14002
>                 URL: https://issues.apache.org/jira/browse/HIVE-14002
>             Project: Hive
>          Issue Type: Improvement
>          Components: Physical Optimizer
>    Affects Versions: 2.2.0
>            Reporter: Nita Dembla
>            Assignee: Jesus Camacho Rodriguez
>         Attachments: HIVE-14002.patch
>
>
> In some occasions, for instance when RS dedup does not kick in, it is useful to propagate
the limit to subsequent RS operators, as this will reduce intermediary results and impact
performance. This issue covers that extension.



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