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https://issues.apache.org/jira/browse/HIVE-20333?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gopal V resolved HIVE-20333.
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Resolution: Duplicate
> CBO: Join removal based on PK-FK declared constraints
> -----------------------------------------------------
>
> Key: HIVE-20333
> URL: https://issues.apache.org/jira/browse/HIVE-20333
> Project: Hive
> Issue Type: Bug
> Reporter: Gopal V
> Priority: Major
>
> A query of the following shape can have its customer join removed entirely on
> the basis of the key containment between customer & store_sales.
> {code}
> select c_customer_sk,sum(ss_quantity*ss_sales_price) ssales from store_sales
> ,customer where ss_customer_sk = c_customer_sk group by c_customer_sk;
> {code}
> This query after join removal can be encoded in as
> {code}
> select ss_customer_sk as c_customer_sk,sum(ss_quantity*ss_sales_price) ssales
> from store_sales where ss_customer_sk is not null group by ss_customer_sk;
> {code}
> The rewrite is not applied today and the current PK-FK relationship does not
> allow for a nullable relationship (i.e a declared Foreign Key can't be NULL).
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