Zhan Zhang created SPARK-11705:
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Summary: 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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