Sergey Nuyanzin created CALCITE-7754:
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Summary: CorrelateProjectExtractor corrupts plans with nested
Correlates that reuse the same correlation id
Key: CALCITE-7754
URL: https://issues.apache.org/jira/browse/CALCITE-7754
Project: Calcite
Issue Type: Bug
Components: core
Reporter: Sergey Nuyanzin
Assignee: Sergey Nuyanzin
{{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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