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From "Adam Kramer (JIRA)" <>
Subject [jira] Created: (HIVE-549) UNION ALL statements should be run in parallel
Date Mon, 08 Jun 2009 07:46:07 GMT
UNION ALL statements should be run in parallel

                 Key: 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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