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https://issues.apache.org/jira/browse/CALCITE-5646?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17713237#comment-17713237
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Leonid Chistov commented on CALCITE-5646:
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I agree that {{Strong class}} API is not perfectly clear and you have to read
the code to understand its semantics.
But for me it is out of scope for current Jira Issue, TBH.
> JoinDeriveIsNotNullFilterRule incorrectly handles COALESCE in join condition
> ----------------------------------------------------------------------------
>
> Key: CALCITE-5646
> URL: https://issues.apache.org/jira/browse/CALCITE-5646
> Project: Calcite
> Issue Type: Bug
> Affects Versions: 1.34.0
> Reporter: Leonid Chistov
> Assignee: Leonid Chistov
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Consider query
> {code:java}
> select t1.deptno from empnullables t1 inner join
> empnullables t2 on coalesce(t1.ename, t2.ename) = 'abc' {code}
> When JoinDeriveIsNotNullFilterRule is applied to it, it is incorrectly
> transformed to query plan
> {code:java}
> LogicalProject(DEPTNO=[$7])
> LogicalJoin(condition=[=(CASE(IS NOT NULL($1), $1, $10), 'abc')],
> joinType=[inner])
> LogicalFilter(condition=[IS NOT NULL($1)])
> LogicalTableScan(table=[[CATALOG, SALES, EMPNULLABLES]])
> LogicalFilter(condition=[IS NOT NULL($1)])
> LogicalTableScan(table=[[CATALOG, SALES, EMPNULLABLES]]) {code}
> It is not valid to deduce that join keys from the both sides cannot have null
> values. All that we can deduce from the join condition, is that they cannot
> be null in the same time.
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