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https://issues.apache.org/jira/browse/HIVE-549?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chaitanya Mishra updated HIVE-549:
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Affects Version/s: 0.3.0
Release Note: Adds the feature of launching multiple map-reduce tasks
that are not dependent on each other in parallel. Examples of queries affected
would be those including union-alls, and trees of join operators.
Status: Patch Available (was: Open)
> 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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