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From "Vineet Garg (JIRA)" <>
Subject [jira] [Created] (HIVE-17493) Improve PKFK cardinality estimation in Physical planning
Date Sat, 09 Sep 2017 00:28:00 GMT
Vineet Garg created HIVE-17493:

             Summary: Improve PKFK cardinality estimation in Physical planning
                 Key: HIVE-17493
             Project: Hive
          Issue Type: Improvement
          Components: Query Planning
            Reporter: Vineet Garg
            Assignee: Vineet Garg

Cardinality estimation of a join, after PK-FK relation has been ascertained, could be improved
if parent of the join operator is LEFT outer or RIGHT outer join.
Currently estimation is done by estimating reduction of rows occurred on PK side, then multiplying
the reduction to FK side row count. This estimation of reduction currently doesn't distinguish
b/w INNER or OUTER joins. This could be improved to handle outer joins better.
TPC-DS query45 is impacted by this.

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