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https://issues.apache.org/jira/browse/HIVE-549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12784385#action_12784385
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Raghotham Murthy commented on HIVE-549:
---------------------------------------

Sorry about jumping into this late. But have you considered using hadoop's 
JobControl? 
http://hadoop.apache.org/common/docs/r0.20.1/api/org/apache/hadoop/mapred/jobcontrol/JobControl.html
 I believe PIG uses it as well.

> Parallel Execution Mechanism
> ----------------------------
>
>                 Key: HIVE-549
>                 URL: https://issues.apache.org/jira/browse/HIVE-549
>             Project: Hadoop Hive
>          Issue Type: Wish
>          Components: Query Processor
>    Affects Versions: 0.3.0
>            Reporter: Adam Kramer
>            Assignee: Chaitanya Mishra
>         Attachments: HIVE549-v6.patch
>
>
> In a massively parallel database system, it would be awesome to also 
> parallelize some of the mapreduce phases that our data needs to go through.
> One example that just occurred to me is UNION ALL: when you union two SELECT 
> statements, effectively you could run those statements in parallel. There's 
> no situation (that I can think of, but I don't have a formal proof) in which 
> the left statement would rely on the right statement, or vice versa. So, they 
> could be run at the same time...and perhaps they should be. Or, perhaps there 
> should be a way to make this happen...PARALLEL UNION ALL? PUNION ALL?

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