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From "Pengcheng Xiong (JIRA)" <>
Subject [jira] [Created] (HIVE-16797) Support a new rule RemoveUnionBranchRule
Date Wed, 31 May 2017 21:54:05 GMT
Pengcheng Xiong created HIVE-16797:

             Summary: Support a new rule RemoveUnionBranchRule
                 Key: HIVE-16797
             Project: Hive
          Issue Type: Bug
            Reporter: Pengcheng Xiong
            Assignee: Pengcheng Xiong

in query4.q, we can see that it creates a CTE with union all of 3 branches. Then it is going
to do a 3 way self-join of the CTE with predicates. The predicates actually specifies only
one of the branch in CTE to participate in the join. Thus, in some cases, e.g.,
               /- filter(false) -----TS0 
union all  - filter(false) -----TS1
we can cut the branches of TS0 and TS1. The union becomes only TS2.

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