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https://issues.apache.org/jira/browse/HIVE-12017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14998913#comment-14998913
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Jesus Camacho Rodriguez commented on HIVE-12017:
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Thanks a lot for the comments [~ashutoshc] and for categorizing the changes.
1) should not be a big issue, at least for the moment.
3) should be an issue only if it is really a performance loss. For instance, I
check some plans and what was happening was that transitive propagation was
more advanced in Calcite, thus we were pruning both join inputs and we ended up
with a cartesian product.
I agree 2) and 5) are specially concerning, since they lead to correctness
issues; I'll explore those ones further and update the issue/create new issues.
At least the fixes to correctness issues should be checked in before applying
this patch.
> 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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