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From "Phabricator (JIRA)" <>
Subject [jira] [Commented] (HIVE-2340) optimize orderby followed by a groupby
Date Wed, 30 Jan 2013 21:07:14 GMT


Phabricator commented on HIVE-2340:

hagleitn has commented on the revision "HIVE-2340 [jira] optimize orderby followed by a groupby".

  Partial review

  common/src/java/org/apache/hadoop/hive/conf/ Not sure why this is needed
or why this defaults to 4. From comment below it seems this is just to avoid the single reducer
order-by case for performance reasons, is that correct?
  ql/src/java/org/apache/hadoop/hive/ql/optimizer/ Is this
required or extra protection? Comment at the top of the file says mapjoin optimization happens
before this (and probably should for performance reasons). Also, if I understand it correctly
"joinAndSort" might be a better name than "fixed". You're basically saying that if an optimization
wants to change the join after this they need to make sure the ordering of the keys is preserved,
  ql/src/java/org/apache/hadoop/hive/ql/ppd/ seems orthogonal
to this patch.
  ql/src/test/queries/clientpositive/reduce_deduplicate.q:7 There are not a lot of tests,
for min.reducer=1. No order by case for instance. Maybe the reduce_deduplicate_extended.q
should run with both default and min.reducer=1.


To: JIRA, navis
Cc: hagleitn

> optimize orderby followed by a groupby
> --------------------------------------
>                 Key: HIVE-2340
>                 URL:
>             Project: Hive
>          Issue Type: Sub-task
>          Components: Query Processor
>            Reporter: Navis
>            Assignee: Navis
>            Priority: Minor
>              Labels: perfomance
>         Attachments: ASF.LICENSE.NOT.GRANTED--HIVE-2340.D1209.1.patch, ASF.LICENSE.NOT.GRANTED--HIVE-2340.D1209.2.patch,
ASF.LICENSE.NOT.GRANTED--HIVE-2340.D1209.5.patch, HIVE-2340.1.patch.txt, HIVE-2340.D1209.6.patch,
HIVE-2340.D1209.7.patch, HIVE-2340.D1209.8.patch, HIVE-2340.D1209.9.patch, testclidriver.txt
> Before implementing optimizer for JOIN-GBY, try to implement RS-GBY optimizer(cluster-by
following group-by).

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