[jira] [Commented] (HIVE-9392) JoinStatsRule miscalculates join cardinality as incorrect NDV is used due to column names having duplicated fqColumnName

["Pengcheng Xiong (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-9392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14521792#comment-14521792 ] 

Pengcheng Xiong commented on HIVE-9392:
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[~prasanth_j] and [~mohammedmostafa], could u plz let [~jpullokkaran] and I know if it is resolved already or it needs further efforts? thanks.

> JoinStatsRule miscalculates join cardinality as incorrect NDV is used due to column names having duplicated fqColumnName
> ------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-9392
>                 URL: https://issues.apache.org/jira/browse/HIVE-9392
>             Project: Hive
>          Issue Type: Bug
>          Components: Physical Optimizer
>    Affects Versions: 0.14.0
>            Reporter: Mostafa Mokhtar
>            Assignee: Prasanth Jayachandran
>            Priority: Critical
>         Attachments: HIVE-9392.1.patch, HIVE-9392.2.patch
>
>
> In JoinStatsRule.process the join column statistics are stored in HashMap  joinedColStats, the key used which is the ColStatistics.fqColName is duplicated between join column in the same vertex, as a result distinctVals ends up having duplicated values which negatively affects the join cardinality estimation.
> The duplicate keys are usually named KEY.reducesinkkey0.



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