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From "Vineet Garg (Jira)" <j...@apache.org>
Subject [jira] [Resolved] (HIVE-24087) FK side join elimination in presence of PK-FK constraint
Date Tue, 01 Sep 2020 15:17:00 GMT

     [ https://issues.apache.org/jira/browse/HIVE-24087?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vineet Garg resolved HIVE-24087.
--------------------------------
    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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