[jira] [Work started] (HIVE-17040) Join elimination in the presence of FK relationship

["Jesus Camacho Rodriguez (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-17040?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Work on HIVE-17040 started by Jesus Camacho Rodriguez.
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> 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
>
> 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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