Vineet Garg created HIVE-17767:
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Summary: Rewrite correlated EXISTS/IN subqueries into LEFT SEMI
JOIN
Key: HIVE-17767
URL: https://issues.apache.org/jira/browse/HIVE-17767
Project: Hive
Issue Type: Improvement
Components: Query Planning
Reporter: Vineet Garg
Assignee: Vineet Garg
Currently such queries are written into group by + inner join with value
generator and is inefficient. Value generator consists of join with outer query
to fetch all correlated values. This value generator could be completely
eliminated if such queries are instead rewritten into LEFT SEMI JOIN.
Note that to do this first hive need to support LEFT SEMI JOIN with non-equi
condition (HIVE-17766).
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