[jira] Updated: (HIVE-549) Parallel Execution Mechanism

["Namit Jain (JIRA)" <ji...@apache.org>]

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

Namit Jain updated HIVE-549:
----------------------------

    Summary: Parallel Execution Mechanism  (was: UNION ALL statements should be run in parallel)

> 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
>
> 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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