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https://issues.apache.org/jira/browse/SPARK-17298?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15446988#comment-15446988
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Sameer Agarwal commented on SPARK-17298:
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Sean, if I understand correctly, here are the new semantics Srinath is
proposing:
1. Case 1: spark.sql.crossJoin.enabled = false
(a) select * from A inner join B *throws an error*
(b) select * from A cross join B *doesn't throw an error*
2. Case 2: spark.sql.crossJoin.enabled = true
(a) select * from A inner join B *doesn't throw an error*
(b) select * from A cross join B *doesn't throw an error*
1(a) and 2(a) confirm with the existing semantics in Spark. This PR proposes
1(b) and 2(b).
> Require explicit CROSS join for cartesian products
> --------------------------------------------------
>
> 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.
> 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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