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