spark-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Xiao Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-11705) Eliminate unnecessary Cartesian Join
Date Sat, 28 Nov 2015 08:58:10 GMT

    [ https://issues.apache.org/jira/browse/SPARK-11705?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15030435#comment-15030435
] 

Xiao Li commented on SPARK-11705:
---------------------------------

[~zzhan] You do not want to fix it by yourself? : )

> 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.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscribe@spark.apache.org
For additional commands, e-mail: issues-help@spark.apache.org


Mime
View raw message