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https://issues.apache.org/jira/browse/HIVE-988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12796966#action_12796966
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Namit Jain commented on HIVE-988:
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Also, is there a race condition which we are missing ? If the last mapper
throws a fatal error, can we miss it since rj is complete by then.
> mapjoin should throw an error if the input is too large
> -------------------------------------------------------
>
> Key: HIVE-988
> URL: https://issues.apache.org/jira/browse/HIVE-988
> Project: Hadoop Hive
> Issue Type: New Feature
> Components: Query Processor
> Reporter: Namit Jain
> Assignee: Ning Zhang
> Fix For: 0.5.0
>
> Attachments: HIVE-988.patch, HIVE-988_2.patch
>
>
> If the input to the map join is larger than a specific threshold, it may lead
> to a very slow execution of the join.
> It is better to throw an error, and let the user redo his query as a non
> map-join query.
> However, the current map-reduce framework will retry the mapper 4 times
> before actually killing the job.
> Based on a offline discussion with Dhruba, Ning and myself, we came up with
> the following algorithm:
> Keep a threshold in the mapper for the number of rows to be processed for
> map-join. If the number of rows
> exceeds that threshold, set a counter and kill that mapper.
> The client (ExecDriver) monitors that job continuously - if this counter is
> set, it kills the job and also
> shows an appropriate error message to the user, so that he can retry the
> query without the map join.
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