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https://issues.apache.org/jira/browse/HIVE-17040?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jesus Camacho Rodriguez updated HIVE-17040:
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Attachment: HIVE-17040.patch
> Join elimination in the presence of FK relationship
> ---------------------------------------------------
>
> Key: HIVE-17040
> URL: https://issues.apache.org/jira/browse/HIVE-17040
> Project: Hive
> Issue Type: Sub-task
> Components: Logical Optimizer
> Affects Versions: 3.0.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Priority: Major
> Attachments: HIVE-17040.patch
>
>
> If the PK/UK table is not filtered, we can safely remove the join.
> A simple example:
> {code:sql}
> SELECT c_current_cdemo_sk
> FROM customer, customer_address
> ON c_current_addr_sk = ca_address_sk;
> {code}
> As a Calcite rule, we could implement this rewriting by 1) matching a Project
> on top of a Join operator, 2) checking that only columns from the FK are used
> in the Project, 3) checking that the join condition matches the FK - PK/UK
> relationship, 4) pulling all the predicates from the PK/UK side and checking
> that the input is not filtered, and 5) removing the join, possibly adding a
> IS NOT NULL condition on the join column from the FK side.
> If the PK/UK table is filtered, we should still transform the Join into a
> SemiJoin operator.
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