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https://issues.apache.org/jira/browse/HIVE-24087?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vineet Garg resolved HIVE-24087.
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Fix Version/s: 4.0.0
Resolution: Fixed
> FK side join elimination in presence of PK-FK constraint
> --------------------------------------------------------
>
> Key: HIVE-24087
> URL: https://issues.apache.org/jira/browse/HIVE-24087
> Project: Hive
> Issue Type: Improvement
> Components: Query Planning
> Reporter: Vineet Garg
> Assignee: Vineet Garg
> Priority: Major
> Labels: pull-request-available
> Fix For: 4.0.0
>
> Time Spent: 1h 10m
> Remaining Estimate: 0h
>
> If there is PK-FK join FK join could be eliminated by removing FK side if
> following conditions are met
> * There is no row filtering on FK side.
> * No columns from FK side is required after JOIN.
> * FK join columns are guranteed to be unique (have group by)
> * FK join columns are guranteed to be NOT NULL (either IS NOT NULL filter or
> constraint)
> *Example*
> {code:sql}
> EXPLAIN
> SELECT customer_removal_n0.*
> FROM customer_removal_n0
> JOIN
> (SELECT lo_custkey
> FROM lineorder_removal_n0
> WHERE lo_custkey IS NOT NULL
> GROUP BY lo_custkey) fkSide ON fkSide.lo_custkey =
> customer_removal_n0.c_custkey;
> {code}
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