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https://issues.apache.org/jira/browse/SPARK-17298?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15446920#comment-15446920
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Srinath commented on SPARK-17298:
---------------------------------
So if I do the following:
create temporary view nt1 as select * from values
("one", 1),
("two", 2),
("three", 3)
as nt1(k, v1);
create temporary view nt2 as select * from values
("one", 1),
("two", 22),
("one", 5)
as nt2(k, v2);
SELECT * FROM nt1, nt2; -- or
select * FROM nt1 inner join nt2;
The SELECT queries do not in fact result in an error. The proposed change would
have them return an error
> 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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