Details
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Bug
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Status: Resolved
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Major
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Resolution: Fixed
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None
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None
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None
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Added new config parameter 'hive.exec.check.crossproducts' to warn about Cross Products. By default this check is on.
Description
Now that we support old style join syntax, it is easy to write queries that generate a plan with a cross product.
For e.g. say you have A join B join C join D on A.x = B.x and A.y = D.y and C.z = D.z
So the JoinTree is:
A — B
|__ D — C
Since we don't reorder join graphs, we will end up with a cross product between (A join B) and C