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From "Pengcheng Xiong (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-9392) JoinStatsRule miscalculates join cardinality as incorrect NDV is used due to column names having duplicated fqColumnName
Date Wed, 06 May 2015 16:34:01 GMT

     [ https://issues.apache.org/jira/browse/HIVE-9392?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Pengcheng Xiong updated HIVE-9392:
----------------------------------
    Attachment:     (was: HIVE-9392.4.patch)

> 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: Pengcheng Xiong
>            Priority: Critical
>         Attachments: HIVE-9392.1.patch, HIVE-9392.2.patch, HIVE-9392.3.patch, HIVE-9392.4.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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