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From "Ning Zhang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-963) no out of memory errors for skewed join
Date Wed, 02 Dec 2009 04:45:20 GMT

    [ https://issues.apache.org/jira/browse/HIVE-963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12784626#action_12784626
] 

Ning Zhang commented on HIVE-963:
---------------------------------

I think we can define a class implementing the Map interface as a wrapper of HashMap and JDBM
HTree, so that map-side join can also use this class rather than using JDBM unconditionally.
It is also easier if we decided to replace JDBM with a simpler and more efficient persistent
hash implementation.

> 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: He Yongqiang
>
> 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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