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https://issues.apache.org/jira/browse/SPARK-11705?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15715675#comment-15715675
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Andrew Ray commented on SPARK-11705:
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Above example does not have a cartesian product in Spark 2.0.2
> 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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