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[CALCITE-7753] CorrelateProjectExtractor corrupts plans with nested Correlates that reuse the same correlation id #5231

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[CALCITE-7753] CorrelateProjectExtractor corrupts plans with nested Correlates that reuse the same correlation id #5231

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[CALCITE-7753] `CorrelateProjectExtractor` corrupts plans with nested…
snuyanzin Aug 29, 2026
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[CALCITE-7754] Address feedback
snuyanzin Sep 15, 2026
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6 changes: 6 additions & 0 deletions core/src/main/java/org/apache/calcite/sql2rel/CorrelateProjectExtractor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@

import org.apache.calcite.rel.RelHomogeneousShuttle;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.Correlate;
import org.apache.calcite.rel.core.CorrelationId;
import org.apache.calcite.rel.core.Filter;
import org.apache.calcite.rel.core.Project;
Expand Down Expand Up @@ -208,6 +209,11 @@ private static Set<RexNode> findCorrelationDependentCalls(CorrelationId corrId,
SimpleCorrelationCollector finder = new SimpleCorrelationCollector(corrId);
plan.accept(new RelHomogeneousShuttle() {
@Override public RelNode visit(RelNode other) {
// Don't descend into a nested correlate that reuses this id: the refs below belong to it.
if (other instanceof Correlate
&& ((Correlate) other).getCorrelationId().equals(corrId)) {
return other;
}
if (other instanceof Project || other instanceof Filter) {
other.accept(finder);
}
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39 changes: 39 additions & 0 deletions core/src/test/java/org/apache/calcite/sql2rel/RelDecorrelatorTest.java
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Expand Up @@ -2548,4 +2548,43 @@ private RelNode decorrelateSql(String sql) {
+ " LogicalTableScan(table=[[bookstore, authors]])\n";
assertThat(after, hasTree(planAfter));
}

/** Test case for
* <a href="https://issues.apache.org/jira/browse/CALCITE-7753">[CALCITE-7753]
* CorrelateProjectExtractor corrupts plans with nested Correlates that reuse
* the same correlation id</a>. */
@Test void testNestedCorrelatesSharingCorrelationId() {

@snuyanzin snuyanzin Aug 29, 2026

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As mentioned in jira: it is not reproducible with pure SQL in Calcite

@snuyanzin snuyanzin Aug 29, 2026

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Because the bug requires two nested Correlates that share the same correlation id, and pure SQL (in Calcite) never produces that shape: Calcite's SqlToRelConverter gives every correlated subquery scope its own id.

final RelBuilder builder = RelBuilder.create(config().build())
.transform(c -> c.withSimplify(false));
final Holder<@Nullable RexCorrelVariable> v = Holder.empty();
builder.scan("EMP").variable(v::set);
final RelNode emp = builder.build();

final RelNode inner = builder
.scan("EMP")
.scan("EMP")
.filter(builder.equals(builder.field(v.get(), "DEPTNO"), builder.field("DEPTNO")))
.correlate(JoinRelType.INNER, v.get().id, builder.field(2, 0, "DEPTNO"))
.filter(builder.isNull(builder.field(v.get(), "COMM")))
.build();

final RelNode before = builder
.push(emp)
.push(inner)
.correlate(JoinRelType.LEFT, v.get().id, builder.field(2, 0, "COMM"))
.build();
final String planBefore = ""
+ "LogicalCorrelate(correlation=[$cor0], joinType=[left], requiredColumns=[{6}])\n"
+ " LogicalTableScan(table=[[scott, EMP]])\n"
+ " LogicalFilter(condition=[IS NULL($cor0.COMM)])\n"
+ " LogicalCorrelate(correlation=[$cor0], joinType=[inner], requiredColumns=[{7}])\n"
+ " LogicalTableScan(table=[[scott, EMP]])\n"
+ " LogicalFilter(condition=[=($cor0.DEPTNO, $7)])\n"
+ " LogicalTableScan(table=[[scott, EMP]])\n";
assertThat(before, hasTree(planBefore));

RelDecorrelator.decorrelateQuery(before, builder,
RuleSets.ofList(Collections.emptyList()),
RuleSets.ofList(Collections.emptyList()));
}
}
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