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https://issues.apache.org/jira/browse/CALCITE-5646?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17714310#comment-17714310
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Leonid Chistov commented on CALCITE-5646:
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Sorry, I don't really understand your point. It looks like you propose new
potential optimization rule "pushdown of IS NULL filter from Join condition",
while this Jira Issue describes bug in "pushdown of IS NOT NULL filter from
Join condition"".
> 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: 20m
> 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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