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https://issues.apache.org/jira/browse/HIVE-8518?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14177840#comment-14177840
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Xuefu Zhang commented on HIVE-8518:
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Okay. Thanks for the explanation.
+1
> Compile time skew join optimization returns duplicated results
> --------------------------------------------------------------
>
> Key: HIVE-8518
> URL: https://issues.apache.org/jira/browse/HIVE-8518
> Project: Hive
> Issue Type: Bug
> Reporter: Rui Li
> Assignee: Rui Li
> Attachments: HIVE-8518.1.patch
>
>
> Compile time skew join optimization clones the join operator tree and unions
> the results.
> The problem here is that we don't properly insert the predicate for the
> cloned join (relying on an assert statement).
> To reproduce the issue, run the simple query:
> {code}select * from tbl1 join tbl2 on tbl1.key=tbl2.key;{code}
> And suppose there's some skew in tbl1 (specify skew with CREATE or ALTER
> statement).
> Duplicated results will be returned if you set
> hive.optimize.skewjoin.compiletime=true.
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