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https://issues.apache.org/jira/browse/SPARK-17298?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15447642#comment-15447642
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Srinath commented on SPARK-17298:
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I've updated the description. Hopefully it is clearer.
Note that before this change, even with spark.sql.crossJoin.enabled = false,
case 1.a may sometimes NOT throw an error (i.e. execute successfully) depending
on the physical plan chosen.
With the proposed change, it would always throw an error
> Require explicit CROSS join for cartesian products by default
> -------------------------------------------------------------
>
> Key: SPARK-17298
> URL: https://issues.apache.org/jira/browse/SPARK-17298
> Project: Spark
> Issue Type: Story
> Components: SQL
> Reporter: Srinath
> Priority: Minor
>
> Require the use of CROSS join syntax in SQL (and a new crossJoin DataFrame
> API) to specify explicit cartesian products between relations under the
> default configuration (spark.sql.crossJoin.enabled = false).
> By cartesian product we mean a join between relations R and S where there is
> no join condition involving columns from both R and S.
> If a cartesian product is detected in the absence of an explicit CROSS join,
> an error must be thrown.
> Turning on the spark.sql.crossJoin.enabled configuration flag will disable
> this check and allow cartesian products without an explicit cross join.
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