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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-948) more query plan optimization rules
Date Sun, 10 Feb 2013 09:15:13 GMT

    [ https://issues.apache.org/jira/browse/HIVE-948?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13575403#comment-13575403
] 

Ashutosh Chauhan commented on HIVE-948:
---------------------------------------

Comments on phabricator.
                
> more query plan optimization rules 
> -----------------------------------
>
>                 Key: HIVE-948
>                 URL: https://issues.apache.org/jira/browse/HIVE-948
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Ning Zhang
>            Assignee: Navis
>         Attachments: HIVE-948.D8463.1.patch
>
>
> Many query plans are not optimal in that they contain redundant operators. Some examples
are unnecessary select operators (select followed by select, select output being the same
as input etc.). Even though these operators are not very expensive, they could account for
around 10% of CPU time in some simple queries. It seems they are low-hanging fruits that we
should pick first. 
> BTW, it seems these optimization rules should be added at the last stage of the physical
optimization phase since some redundant operators are added to facilitate physical plan generation.


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