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Date: Sun, 1 Nov 2009 23:02:59 +0000 (UTC)
From: "Zheng Shao (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
Subject: [jira] Commented: (HIVE-549) Parallel Execution Mechanism
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    [ https://issues.apache.org/jira/browse/HIVE-549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12772385#action_12772385 ] 

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

THIVE-549-v3.patch:
Can you add javadoc comments to all public methods (except getters and setters)? I know we were not following that all the time historically, but we want to enforce that on all new patches.

It seems to me that "shouldLaunch()" is a better name than "checkLaunch()", but it's up to you whether you would like to change it.

Can we change the name of "hive.optimize.par" to "hive.execution.parallel"?
"optimize" was meant for plan optimization. This is an execution time option. Also "par" does not reflect to "parallel" in my mind.


> 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-v3.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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