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From "Jesus Camacho Rodriguez (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-11684) Implement limit pushdown through outer join in CBO
Date Fri, 11 Sep 2015 10:09:46 GMT

    [ https://issues.apache.org/jira/browse/HIVE-11684?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14740519#comment-14740519
] 

Jesus Camacho Rodriguez commented on HIVE-11684:
------------------------------------------------

[~sershe], QA fails are not related to the patch, it is just pending review, so it should
go in soon; this work is done on master.

{quote}
Actually, I wonder if some CBO features should be disable-able via configs, like existing
Hive optimizations. Should I file a JIRA for that?
{quote}
I don't know if we want to go in that direction in the long term, but maybe in the short term
we could do that instead of disabling CBO by default for these cases. [~jpullokkaran], what's
your take on that?
IMO, we should be able to recognize automatically these cases instead of introducing more
config parameters: if we can match a certain criteria e.g. query with 2 joins whose selectivity
is very similar, do not fire up certain logic in CBO (join reordering, or maybe some other
rules). In fact, it would be necessary to combine static (query) with dynamic (data) information
in order to make these decisions accurately. At the same time, the logic should be lightweight
enough to not add much more overhead to the planning phase, otherwise it would be cheaper
to run the complete CBO path...

> Implement limit pushdown through outer join in CBO
> --------------------------------------------------
>
>                 Key: HIVE-11684
>                 URL: https://issues.apache.org/jira/browse/HIVE-11684
>             Project: Hive
>          Issue Type: New Feature
>          Components: CBO
>    Affects Versions: 2.0.0
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Jesus Camacho Rodriguez
>         Attachments: HIVE-11684.01.patch, HIVE-11684.02.patch, HIVE-11684.03.patch, HIVE-11684.04.patch,
HIVE-11684.05.patch, HIVE-11684.patch
>
>




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