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https://issues.apache.org/jira/browse/HIVE-19770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16508888#comment-16508888
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Vineet Garg commented on HIVE-19770:
------------------------------------
bq. One query has different (worse) plan (it now has cbo + vectorization) and
new plan for some reason contains extra reducer. The root cause for this has
yet to be determined but this should not introduce correctness issues.
This query consist of group by + bunch of PTF operations. Earlier in non-cbo
PTF was done on reduce side because mapper partition key was same as PTF key
but now PTF is done in separate vertex/reducer because partition key is changed
to contain all group by keys. Semantically this is correct but not optimized.
I'll open a JIRA to track this.
> Support for CBO for queries with multiple same columns in select
> ----------------------------------------------------------------
>
> Key: HIVE-19770
> URL: https://issues.apache.org/jira/browse/HIVE-19770
> Project: Hive
> Issue Type: Improvement
> Reporter: Vineet Garg
> Assignee: Vineet Garg
> Priority: Major
> Attachments: HIVE-19770.1.patch, HIVE-19770.2.patch
>
>
> Currently queries such as {code:sql} select a,a from t1 where b > 10 {code}
> are not supported for CBO.
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