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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-963) no out of memory errors for skewed join
Date Wed, 16 Dec 2009 06:34:18 GMT

    [ https://issues.apache.org/jira/browse/HIVE-963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12791231#action_12791231
] 

Namit Jain commented on HIVE-963:
---------------------------------

looks good - 1 minor comment.
Dont you need to clean up the temp files at the beginning of each group.

    for ( ArrayListWrapper alw: storage.values() )
      alw.clear(); // clean up the temp files                                            
   
    storage.clear();

Isn't this needed in startGroup() also ?




> no out of memory errors for skewed join
> ---------------------------------------
>
>                 Key: HIVE-963
>                 URL: https://issues.apache.org/jira/browse/HIVE-963
>             Project: Hadoop Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Ning Zhang
>         Attachments: HIVE-963.patch
>
>
> Currently, in case of skew, hive runs out of memory.
> A simpler fix would be to use JDBM to store data and use that.
> It can be configurable and JDBM should only be triggered if the number of values for
a given key exceed a given number.

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