Pengcheng Xiong created HIVE-16797:
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Summary: Support a new rule RemoveUnionBranchRule
Key: HIVE-16797
URL: https://issues.apache.org/jira/browse/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.,
{code}
/- filter(false) -----TS0
union all - filter(false) -----TS1
\-----TS2
{code}
we can cut the branches of TS0 and TS1. The union becomes only TS2.
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