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Posted to dev@hive.apache.org by "Vineet Garg (JIRA)" <ji...@apache.org> on 2017/09/09 00:28:00 UTC

[jira] [Created] (HIVE-17493) Improve PKFK cardinality estimation in Physical planning

Vineet Garg created HIVE-17493:
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             Summary: Improve PKFK cardinality estimation in Physical planning
                 Key: HIVE-17493
                 URL: https://issues.apache.org/jira/browse/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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