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https://issues.apache.org/jira/browse/CALCITE-7702?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mihai Budiu resolved CALCITE-7702.
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Fix Version/s: 1.43.0
Resolution: Fixed
Fixed in
[https://github.com/apache/calcite/commit/dd067b6f9292eb828c5bb1c6d9c134872d3ffae9]
Thank you for the report and fix [~zzwqqq]
> JoinAggregateTransposeRule produces a non-equivalent plan when the aggregate
> with empty input and empty group set
> -----------------------------------------------------------------------------------------------------------------
>
> Key: CALCITE-7702
> URL: https://issues.apache.org/jira/browse/CALCITE-7702
> Project: Calcite
> Issue Type: Bug
> Reporter: zzwqqq
> Assignee: zzwqqq
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.43.0
>
>
> JoinAggregateTransposeRule produces a non-equivalent plan when the aggregate
> with empty input empty group set
> For example, using the SCOTT schema:
> {code:sql}
> select g.emp_count, d.deptno
> from (select count(*) as emp_count from emp where false) g
> join (select deptno from dept where deptno = 10) d on true;
> {code}
> The query returns:
> {code:java}
> emp_count | deptno
> -----------+--------
> 0 | 10
> (1 row)
> {code}
> The rewritten plan has the same behavior as follow，and returns no rows:
> {code:sql}
> select count(*) as emp_count, d.deptno
> from (select * from emp where false) e
> join (select deptno from dept where deptno = 10) d on true
> group by d.deptno;
> {code}
> COUNT without GROUP BY returns one row for empty input. After the aggregate
> is pulled above the join, DEPTNO becomes a group key. An aggregate with a
> group key returns no rows for empty input.
> The rule should not apply in this case unless the aggregate input is known to
> be non-empty.
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