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From "Chaitanya Mishra (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HIVE-549) Parallel Execution Mechanism
Date Wed, 04 Nov 2009 00:41:32 GMT

     [ https://issues.apache.org/jira/browse/HIVE-549?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chaitanya Mishra updated HIVE-549:
----------------------------------

    Attachment: HIVE-549-v4.patch

Thanks for the comments.

- Renamed variable to hive.exec.parallel
- Renamed function to shouldLaunch
- Added javadocs for a few functions
- The task information remains of the form (Stage-x) as before.
- However, for each new Map-reduce job launched, I print a sentence of the form "Launching
job 3 out of 5". Note that this is only for map-reduce jobs.

I don't have a good answer for the exception question, since I don't quite know what Hive
did before.

Comments?

> 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, 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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