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Convert left correlated join to inner join during transformation #19922

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Nov 27, 2023
Merged

Convert left correlated join to inner join during transformation #19922

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13 changes: 10 additions & 3 deletions ...rc/main/java/io/trino/sql/planner/iterative/rule/TransformUncorrelatedSubqueryToJoin.java
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
import io.trino.matching.Pattern;
import io.trino.spi.type.Type;
import io.trino.sql.planner.Symbol;
import io.trino.sql.planner.iterative.Lookup;
import io.trino.sql.planner.iterative.Rule;
import io.trino.sql.planner.plan.Assignments;
import io.trino.sql.planner.plan.CorrelatedJoinNode;
Expand All @@ -36,6 +37,7 @@
import static com.google.common.base.Preconditions.checkState;
import static io.trino.matching.Pattern.empty;
import static io.trino.sql.analyzer.TypeSignatureTranslator.toSqlType;
import static io.trino.sql.planner.optimizations.QueryCardinalityUtil.extractCardinality;
import static io.trino.sql.planner.plan.CorrelatedJoinNode.Type.FULL;
import static io.trino.sql.planner.plan.CorrelatedJoinNode.Type.INNER;
import static io.trino.sql.planner.plan.CorrelatedJoinNode.Type.LEFT;
Expand Down Expand Up @@ -64,7 +66,8 @@ public Result apply(CorrelatedJoinNode correlatedJoinNode, Captures captures, Co
return Result.ofPlanNode(rewriteToJoin(
correlatedJoinNode,
correlatedJoinNode.getType().toJoinNodeType(),
correlatedJoinNode.getFilter()));
correlatedJoinNode.getFilter(),
context.getLookup()));
}

checkState(
Expand All @@ -79,7 +82,7 @@ public Result apply(CorrelatedJoinNode correlatedJoinNode, Captures captures, Co
else {
type = JoinNode.Type.LEFT;
}
JoinNode joinNode = rewriteToJoin(correlatedJoinNode, type, TRUE_LITERAL);
JoinNode joinNode = rewriteToJoin(correlatedJoinNode, type, TRUE_LITERAL, context.getLookup());

if (correlatedJoinNode.getFilter().equals(TRUE_LITERAL)) {
return Result.ofPlanNode(joinNode);
Expand Down Expand Up @@ -109,8 +112,12 @@ public Result apply(CorrelatedJoinNode correlatedJoinNode, Captures captures, Co
return Result.empty();
}

private JoinNode rewriteToJoin(CorrelatedJoinNode parent, JoinNode.Type type, Expression filter)
private JoinNode rewriteToJoin(CorrelatedJoinNode parent, JoinNode.Type type, Expression filter, Lookup lookup)
{
if (type == JoinNode.Type.LEFT && extractCardinality(parent.getSubquery(), lookup).isAtLeastScalar() && filter.equals(TRUE_LITERAL)) {
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// input rows will always be matched against subquery rows
type = JoinNode.Type.INNER;
}
return new JoinNode(
parent.getId(),
type,
Expand Down
25 changes: 22 additions & 3 deletions ...est/java/io/trino/sql/planner/iterative/rule/TestTransformUncorrelatedSubqueryToJoin.java
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,6 @@
import static io.trino.sql.planner.assertions.PlanMatchPattern.project;
import static io.trino.sql.planner.assertions.PlanMatchPattern.values;
import static io.trino.sql.planner.plan.CorrelatedJoinNode.Type.FULL;
import static io.trino.sql.planner.plan.CorrelatedJoinNode.Type.INNER;
import static io.trino.sql.planner.plan.CorrelatedJoinNode.Type.LEFT;
import static io.trino.sql.planner.plan.CorrelatedJoinNode.Type.RIGHT;
import static io.trino.sql.planner.plan.JoinNode.Type;
Expand All @@ -36,6 +35,26 @@
public class TestTransformUncorrelatedSubqueryToJoin
extends BaseRuleTest
{
@Test
public void testRewriteLeftCorrelatedJoinWithScalarSubquery()
{
tester().assertThat(new TransformUncorrelatedSubqueryToJoin())
.on(p -> {
Symbol a = p.symbol("a");
Symbol b = p.symbol("b");
return p.correlatedJoin(
emptyList(),
p.values(a),
LEFT,
TRUE_LITERAL,
p.values(1, b));
})
.matches(
join(Type.INNER, builder -> builder
.left(values("a"))
.right(values("b"))));
}

@Test
public void testRewriteInnerCorrelatedJoin()
{
Expand All @@ -46,15 +65,15 @@ public void testRewriteInnerCorrelatedJoin()
return p.correlatedJoin(
emptyList(),
p.values(a),
INNER,
LEFT,
new ComparisonExpression(
GREATER_THAN,
b.toSymbolReference(),
a.toSymbolReference()),
p.values(b));
})
.matches(
join(Type.INNER, builder -> builder
join(Type.LEFT, builder -> builder
.filter("b > a")
.left(values("a"))
.right(values("b"))));
Expand Down