[HIVE-6643] Add a check for cross products in plans and output a warning

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.13.0
• Release Note: Added new config parameter 'hive.exec.check.crossproducts' to warn about Cross Products. By default this check is on.
• Assignee: Harish Butani
• Reporter: Harish Butani
• Created: 12/Mar/14 23:50
• Updated: 08/Oct/15 02:11
• Resolved: 29/Mar/14 00:03

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