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https://issues.apache.org/jira/browse/CALCITE-3495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16972314#comment-16972314
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Jin Xing commented on CALCITE-3495:
-----------------------------------
By nested loop join, when deptno=0 in dept, it will generate a corresponding
record of 0 from the subquery;
However in the Aggregate of decorrelated plan, there's no chance to generate
such a record of 0;
IMHO we should fail the decorrelation for Aggregate when the child contains
correlated ref but at the same time the Aggregate can generate rows with no
input, e.g. the aggregate function is SUM, COUNT
> RelDecorrelator generate plan with different semantics when handle Aggregate
> ----------------------------------------------------------------------------
>
> Key: CALCITE-3495
> URL: https://issues.apache.org/jira/browse/CALCITE-3495
> Project: Calcite
> Issue Type: Bug
> Reporter: Jin Xing
> Priority: Major
>
> Given below Sql and data
> {code:java}
> SELECT deptno FROM dept A where deptno in
> (SELECT count(1) FROM emp B where A.deptno = B.deptno)
> -----------------------------------------------------
> Data of dept:
> deptno
> 0
> 1
> ----------------
> Data of emp:
> deptno
> 1{code}
> From the Sql semantics by nest-loop join, we will expect the result as
> {code:java}
> Result:
> deptno
> 0
> 1{code}
> However the decorrelated plan is as below:
> {code:java}
> LogicalProject(DEPTNO=[$0])
> LogicalJoin(condition=[=($0, $3)], joinType=[inner])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
> LogicalFilter(condition=[=($1, $0)])
> LogicalProject(EXPR$0=[$1], DEPTNO=[$0])
> LogicalAggregate(group=[{0}], EXPR$0=[COUNT()])
> LogicalProject(DEPTNO=[$7], $f0=[1])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}
> The result of this plan is as below:
> {code:java}
> Result:
> deptno
> 1
> {code}
> As we can see the two above results are different.
>
>
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