Vineet Garg created HIVE-21537:
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Summary: Scalar query rewrite could be improved to not generate an
extra join if subquery is guaranteed to produce atmost one row
Key: HIVE-21537
URL: https://issues.apache.org/jira/browse/HIVE-21537
Project: Hive
Issue Type: Improvement
Components: Query Planning
Affects Versions: 4.0.0
Reporter: Vineet Garg
Assignee: Vineet Garg
Currently Hive planner introduces this branch and later executes a rule to
remove this branch if it could.
Subquery remove rule itself could check if subquery will produce max one row
(using relmetadat's getMaxRowCount) and avoid introducing this branch.
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