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https://issues.apache.org/jira/browse/HIVE-12017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15000487#comment-15000487
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Jesus Camacho Rodriguez commented on HIVE-12017:
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[~ashutoshc], concerning the createProject method, the method with the same
signature in RelOptUtil has a different behavior: it removes the Project if it
is an identity project (line 2799 in RelOptUtil). This was leading to some
problems in Hive, as we were ending up with columns with equal names. I should
add a note to the method in the next version of the patch.
About the additional profile, +1. I had already talked with [~gopalv] about
this. I think the framework implemented in this patch is generic enough to add
without effort any profile in the future, and being able to enable/disable them
easily.
> Do not disable CBO by default when number of joins in a query is equal or
> less than 1
> -------------------------------------------------------------------------------------
>
> Key: HIVE-12017
> URL: https://issues.apache.org/jira/browse/HIVE-12017
> Project: Hive
> Issue Type: Improvement
> Components: CBO
> Affects Versions: 2.0.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Attachments: HIVE-12017.01.patch, HIVE-12017.02.patch,
> HIVE-12017.03.patch, HIVE-12017.04.patch, HIVE-12017.05.patch,
> HIVE-12017.06.patch, HIVE-12017.07.patch, HIVE-12017.08.patch
>
>
> Instead, we could disable some parts of CBO that are not relevant if the
> query contains 1 or 0 joins. Implementation should be able to define easily
> other query patterns for which we might disable some parts of CBO (in case we
> want to do it in the future).
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