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https://issues.apache.org/jira/browse/CALCITE-7753?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18110183#comment-18110183
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Stamatis Zampetakis commented on CALCITE-7753:
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[~Sergey Nuyanzin] can you please add also an example of the invalid plan after
the transformation in the description? I mainly want to understand if its the
extractor class causing the issue or another subsequent transformation in the
decorrelator.
> CorrelateProjectExtractor corrupts plans with nested Correlates that reuse
> the same correlation id
> --------------------------------------------------------------------------------------------------
>
> Key: CALCITE-7753
> URL: https://issues.apache.org/jira/browse/CALCITE-7753
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Sergey Nuyanzin
> Assignee: Sergey Nuyanzin
> Priority: Major
> Labels: pull-request-available
>
> {{CorrelateProjectExtractor}} moves correlated expressions from a correlate's
> right side to its left. If the right side contains a nested correlate reusing
> the same id (e.g. {{$cor0}}), the extractor also grabs the inner references
> and adds them to the outer correlate's {{requiredColumns}}. The decorrelated
> right never produces them, so the plan is inconsistent and
> {{RelDecorrelator}} fails with an {{AssertionError}}.
> Calcite's SQL translation never nests two correlates sharing one id, so it
> isn't reachable from SQL; however downstream planners like Flink build this
> shape.
> Example — outer correlate over {{EMP}} uses {{$cor0.COMM}}, nested correlate
> over {{DEPT}} reuses {{$cor0}} and uses {{$cor0.DEPTNO}}:
> {noformat}
> LogicalCorrelate(correlation=[$cor0], joinType=[left], requiredColumns=[{6}])
> LogicalTableScan(table=[[scott, EMP]])
> LogicalFilter(condition=[IS NULL($cor0.COMM)])
> LogicalCorrelate(correlation=[$cor0], joinType=[inner],
> requiredColumns=[{0}])
> LogicalTableScan(table=[[scott, DEPT]])
> LogicalFilter(condition=[=($cor0.DEPTNO, $7)])
> LogicalTableScan(table=[[scott, EMP]])
> {noformat}
> {{decorrelateQuery}} throws {{AssertionError}}, the same plan with a distinct
> nested id works.
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