[jira] [Commented] (HIVE-6643) Add a check for cross products in plans and output a warning

["Lefty Leverenz (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-6643?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14051220#comment-14051220 ] 

Lefty Leverenz commented on HIVE-6643:
--------------------------------------

*hive.exec.check.crossproducts* is documented in the wiki here:

* [Configuration Properties -- hive.exec.check.crossproducts | https://cwiki.apache.org/confluence/display/Hive/Configuration+Properties#ConfigurationProperties-hive.exec.check.crossproducts]

I added a comment to HIVE-6586 so it won't get lost in the shuffle when HIVE-6037 changes HiveConf.java.

> Add a check for cross products in plans and output a warning
> ------------------------------------------------------------
>
>                 Key: HIVE-6643
>                 URL: https://issues.apache.org/jira/browse/HIVE-6643
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Harish Butani
>            Assignee: Harish Butani
>             Fix For: 0.13.0
>
>         Attachments: HIVE-6643.1.patch, HIVE-6643.2.patch, HIVE-6643.3.patch, HIVE-6643.4.patch, HIVE-6643.5.patch, HIVE-6643.6.patch, HIVE-6643.7.patch
>
>
> Now that we support old style join syntax, it is easy to write queries that generate a plan with a cross product.
> For e.g. say you have A join B join C join D on A.x = B.x and A.y = D.y and C.z = D.z
> So the JoinTree is:
> A — B
> |__  D — C
> Since we don't reorder join graphs, we will end up with a cross product between (A join B) and C



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