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Posted to issues@spark.apache.org by "Reynold Xin (JIRA)" <ji...@apache.org> on 2016/12/02 19:09:58 UTC

[jira] [Closed] (SPARK-11705) Eliminate unnecessary Cartesian Join

     [ https://issues.apache.org/jira/browse/SPARK-11705?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Reynold Xin closed SPARK-11705.
-------------------------------
    Resolution: Cannot Reproduce

> Eliminate unnecessary Cartesian Join
> ------------------------------------
>
>                 Key: SPARK-11705
>                 URL: https://issues.apache.org/jira/browse/SPARK-11705
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Zhan Zhang
>
> When we have some queries similar to following (don’t remember the exact form):
> select * from a, b, c, d where a.key1 = c.key1 and b.key2 = c.key2 and c.key3 = d.key3
> There will be a cartesian join between a and b. But if we just simply change the table order, for example from a, c, b, d, such cartesian join are eliminated.
> Without such manual tuning, the query will never finish if a, b are big. But we should not relies on such manual optimization.



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