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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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zzwqqq reassigned CALCITE-7702:
-------------------------------
Assignee: 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
>
> 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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