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https://issues.apache.org/jira/browse/HIVE-2340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13556651#comment-13556651
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Ashutosh Chauhan commented on HIVE-2340:
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Thanks Yin for explaining. Your ASCII art helped in understanding the
differences : ) I better understand the reason for the fake new operator now. I
think in cases you have pointed out when there is such kind of trees, this
reduce deduplication approach won't help, since it looks at linear chain of RS
and eliminates the one where it could. You would need a fake operator in such
case because you don't want to modify the GBY or Join operators which make
sense. I see the merits of Ysmart better now.
Though, on the other hand patch on this jira is still useful and complementary
to ysmart. Since, it will collapse linear RS, instead of adding fake ones. In
addition to collapsing of those operators, it will also make the life of ysmart
easier because than ysmart will be dealing with simpler plans with reduce sinks
already deduplicated. We need to make sure reducededup rule fires before ysmart
for both optimizations to play nicely. So, I think we should make progress on
both these patches.
[~navis] Will you like to refresh this patch?
> optimize orderby followed by a groupby
> --------------------------------------
>
> Key: HIVE-2340
> URL: https://issues.apache.org/jira/browse/HIVE-2340
> 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.D1209.3.patch,
> ASF.LICENSE.NOT.GRANTED--HIVE-2340.D1209.4.patch,
> ASF.LICENSE.NOT.GRANTED--HIVE-2340.D1209.5.patch, HIVE-2340.1.patch.txt
>
>
> Before implementing optimizer for JOIN-GBY, try to implement RS-GBY
> optimizer(cluster-by following group-by).
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