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From "Namit Jain (JIRA)" <>
Subject [jira] Commented: (HIVE-549) Parallel Execution Mechanism
Date Tue, 24 Nov 2009 01:12:39 GMT


Namit Jain commented on HIVE-549:

Yes, can you do the following:


insert into a temporary table and then select from that order with a order by'

input42.q/input_part9.q: just add a order by

You can do something similar for input* tests - just remember that there are some special
optimizations for map-only union queries which we are testing here.
We want to keep those tests - so instead of adding a order by at the end of union, just insert
into a temporary table and then select from that table order by.

> Parallel Execution Mechanism
> ----------------------------
>                 Key: HIVE-549
>                 URL:
>             Project: Hadoop Hive
>          Issue Type: Wish
>          Components: Query Processor
>            Reporter: Adam Kramer
>            Assignee: Chaitanya Mishra
>         Attachments: HIVE-549-v5.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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