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From "Zheng Shao (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-549) Parallel Execution Mechanism
Date Tue, 10 Nov 2009 18:55:28 GMT

    [ https://issues.apache.org/jira/browse/HIVE-549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12776006#action_12776006
] 

Zheng Shao commented on HIVE-549:
---------------------------------

Hi Chaitanya, the code looks good to me except a small nitch: can you change the logic of
"shouldLaunch()"? Currently it means "shouldNotLaunch()".

After you have done that, please test again with "ant test -logfile log.txt" and make sure
all tests are passing.

Then we can commit it.



> Parallel Execution Mechanism
> ----------------------------
>
>                 Key: HIVE-549
>                 URL: https://issues.apache.org/jira/browse/HIVE-549
>             Project: Hadoop Hive
>          Issue Type: Wish
>          Components: Query Processor
>            Reporter: Adam Kramer
>            Assignee: Chaitanya Mishra
>         Attachments: HIVE-549-v4.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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