Srinath Shankar e6132a6cf1 [SPARK-17298][SQL] Require explicit CROSS join for cartesian products ... ## What changes were proposed in this pull request? 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. The new crossJoin DataFrame API must be used to specify explicit cross joins. The existing join(DataFrame) method will produce a INNER join that will require a subsequent join condition. That is df1.join(df2) is equivalent to select * from df1, df2. ## How was this patch tested? Added cross-join.sql to the SQLQueryTestSuite to test the check for cartesian products. Added a couple of tests to the DataFrameJoinSuite to test the crossJoin API. Modified various other test suites to explicitly specify a cross join where an INNER join or a comma-separated list was previously used. Author: Srinath Shankar <srinath@databricks.com> Closes #14866 from srinathshankar/crossjoin.		2016-09-03 00:20:43 +02:00
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main	[SPARK-17298][SQL] Require explicit CROSS join for cartesian products	2016-09-03 00:20:43 +02:00
test	[SPARK-17298][SQL] Require explicit CROSS join for cartesian products	2016-09-03 00:20:43 +02:00