zzwqqq created CALCITE-7702:
-------------------------------
Summary: 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
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.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
