[jira] [Updated] (HIVE-3972) Support using multiple reducer for fetching order by results

["Navis (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-3972?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Navis updated HIVE-3972:
------------------------

    Attachment: HIVE-3972.8.patch.txt

> Support using multiple reducer for fetching order by results
> ------------------------------------------------------------
>
>                 Key: HIVE-3972
>                 URL: https://issues.apache.org/jira/browse/HIVE-3972
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Navis
>            Assignee: Navis
>            Priority: Minor
>         Attachments: D8349.5.patch, D8349.6.patch, D8349.7.patch, HIVE-3972.8.patch.txt, HIVE-3972.D8349.1.patch, HIVE-3972.D8349.2.patch, HIVE-3972.D8349.3.patch, HIVE-3972.D8349.4.patch
>
>
> Queries for fetching results which have lastly "order by" clause make final MR run with single reducer, which can be too much. For example, 
> {code}
> select value, sum(key) as sum from src group by value order by sum;
> {code}
> If number of reducer is reasonable, multiple result files could be merged into single sorted stream in the fetcher level.



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