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From "Lefty Leverenz (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-16298) Add config to specify multi-column joins have correlated columns
Date Sun, 26 Mar 2017 08:04:41 GMT

     [ https://issues.apache.org/jira/browse/HIVE-16298?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Lefty Leverenz updated HIVE-16298:
----------------------------------
    Labels: TODOC3.0  (was: )

> Add config to specify multi-column joins have correlated columns
> ----------------------------------------------------------------
>
>                 Key: HIVE-16298
>                 URL: https://issues.apache.org/jira/browse/HIVE-16298
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Jason Dere
>            Assignee: Siddharth Seth
>              Labels: TODOC3.0
>             Fix For: 2.2.0
>
>         Attachments: HIVE-16298.1.patch, HIVE-16298.2.patch
>
>
> The default row estimation for multi-key joins divides the row estimate by the product
of the NDVs for each join column, which can cause the row estimate to be low. Try adding a
config to assume the columns are correlated, where we only divide the row estimate by the
largest NDV.



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