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https://issues.apache.org/jira/browse/HIVE-2340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13570813#comment-13570813
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Navis commented on HIVE-2340:
-----------------------------
@Gunther Hagleitner: I also considered ratio thing, but number of reducers is
calculated based on input size just before submitted to hadoop and cannot be
known in optimizer layer.
Except those special cases with order by and bucketing, number of reducers for
both RS is -1. So generally speaking, it's safe.
> optimize orderby followed by a groupby
> --------------------------------------
>
> Key: HIVE-2340
> URL: https://issues.apache.org/jira/browse/HIVE-2340
> Project: Hive
> Issue Type: Sub-task
> Components: Query Processor
> Reporter: Navis
> Assignee: Navis
> Priority: Minor
> Labels: perfomance
> Attachments: ASF.LICENSE.NOT.GRANTED--HIVE-2340.D1209.1.patch,
> ASF.LICENSE.NOT.GRANTED--HIVE-2340.D1209.2.patch,
> ASF.LICENSE.NOT.GRANTED--HIVE-2340.D1209.3.patch,
> ASF.LICENSE.NOT.GRANTED--HIVE-2340.D1209.4.patch,
> ASF.LICENSE.NOT.GRANTED--HIVE-2340.D1209.5.patch, HIVE-2340.1.patch.txt,
> HIVE-2340.D1209.10.patch, HIVE-2340.D1209.6.patch, HIVE-2340.D1209.7.patch,
> HIVE-2340.D1209.8.patch, HIVE-2340.D1209.9.patch, testclidriver.txt
>
>
> Before implementing optimizer for JOIN-GBY, try to implement RS-GBY
> optimizer(cluster-by following group-by).
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