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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-549) Parallel Execution Mechanism
Date Tue, 01 Dec 2009 18:54:20 GMT

    [ https://issues.apache.org/jira/browse/HIVE-549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12784336#action_12784336
] 

Namit Jain commented on HIVE-549:
---------------------------------

I will take a look

> 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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