You are viewing a plain text version of this content. The canonical link for it is here.

Posted to issues@hive.apache.org by "Jason Dere (JIRA)" <ji...@apache.org> on 2017/03/25 01:33:41 UTC

[jira] [Updated] (HIVE-16298) Add config to specify multi-column joins have correlated columns

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

Jason Dere updated HIVE-16298:
------------------------------
    Attachment: HIVE-16298.1.patch

Attaching patch. [~prasanth_j] [~ashutoshc] can you take a look?

> 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: Jason Dere
>         Attachments: HIVE-16298.1.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.



--
This message was sent by Atlassian JIRA
(v6.3.15#6346)