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https://issues.apache.org/jira/browse/CALCITE-5740?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18053703#comment-18053703
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Julian Hyde commented on CALCITE-5740:
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There should be a test and javadoc for the Join node in the query "select
e.sal, e.job, d.dname from emp as e join dept as d on e.deptno = d.deptno". It
used two fields used from the left and one field used from the right. I
*presume* that the field from the right is zero-based but ImmutableBitSet.union
would only do the right thing if it is 7-based (because emp has 7 fields).
> Support for AggToSemiJoinRule
> -----------------------------
>
> Key: CALCITE-5740
> URL: https://issues.apache.org/jira/browse/CALCITE-5740
> Project: Calcite
> Issue Type: New Feature
> Reporter: Rong Rong
> Assignee: Zhen Chen
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.42.0
>
>
> **Description**
> Currently we only have JoinToSemiJoin and ProjectToSemiJoin rule. which in
> the rule itself it performance check and see if the project accesses columns
> from the RHS result
> This can be extended to Aggregate as well, experimental code:
> https://github.com/walterddr/calcite/pull/1/files
> **Alternative**
> Alternative is to add a project/calc between the join and the aggregate to
> activate the project-to-semi-join rule. please share if there's any other
> alternative if I haven't considered.
> thanks
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