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https://issues.apache.org/jira/browse/CALCITE-330?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15713452#comment-15713452
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Julian Hyde commented on CALCITE-330:
-------------------------------------
Since we opted to create {{SemiJoin}} (see CALCITE-368), rather than create the
{{eliminateRightDuplicates}} flag, this case will probably never be fixed.
> Add a rule that converts join-on-aggregate to semi-join
> -------------------------------------------------------
>
> Key: CALCITE-330
> URL: https://issues.apache.org/jira/browse/CALCITE-330
> Project: Calcite
> Issue Type: New Feature
> Reporter: Julian Hyde
> Assignee: Julian Hyde
>
> Once CALCITE-328 is completed and {{Join}} has a flag
> {{eliminateRightDuplicates}}, we need a rule to populate that flag from SQL
> queries.
> Transformers that deal with 'IN subquery' (both correlated and uncorrelated)
> should set this flag. (In particular check TPC-DS Q95.)
> Also queries written '... JOIN (SELECT DISTINCT ...)'.
> Also handle queries whose right input is known to be already unique, e.g.
> {code:sql}
> SELECT emp.name
> FROM emp JOIN dept USING (deptno)
> WHERE dept.location = 'San Francisco'
> {code}
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