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https://issues.apache.org/jira/browse/CALCITE-5201?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Benchao Li reopened CALCITE-5201:
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> Improve SemiJoinRule to match Join's right input which is unique for Join keys
> ------------------------------------------------------------------------------
>
> Key: CALCITE-5201
> URL: https://issues.apache.org/jira/browse/CALCITE-5201
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.30.0
> Reporter: Benchao Li
> Assignee: Benchao Li
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.32.0
>
> Time Spent: 4h 10m
> Remaining Estimate: 0h
>
> As disscussed in CALCITE-5195, the following SQL cannot be transformed to
> semi join:
> {code:sql}
> select *
> from emp
> where exists(select * from dept where emp.deptno = dept.deptno and emp.empno
> = dept.deptno)
> {code}
> Currently {{SemiJoinRule}} requires that right child must be an
> {{Aggregate}}, however, sometimes it's not, e.g. in
> [{{RelBuilder}}|https://github.com/apache/calcite/blob/300f5200fe50870da418366613df1cd09921b1b6/core/src/main/java/org/apache/calcite/tools/RelBuilder.java#L2241-L2247],
> if the group keys are unique, then we'll remove the {{Aggregate}}.
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