HHH-16465 Fix String based CTE cycle emulation

hibernate-core/src/main/java/org/hibernate/sql/ast/spi/AbstractSqlAstTranslator.java

@@ -2489,8 +2489,8 @@ public abstract class AbstractSqlAstTranslator<T extends JdbcOperation> implemen
 		final AbstractSqmSelfRenderingFunctionDescriptor concat = findSelfRenderingFunction( "concat", 2 );
 		final AbstractSqmSelfRenderingFunctionDescriptor coalesce = findSelfRenderingFunction( "coalesce", 2 );
 		final BasicType<String> stringType = getStringType();
-		// Shift by 1 bit instead of multiplying by 2
+		// Shift by 2 bit instead of multiplying by 4
-		final List<SqlAstNode> arguments = new ArrayList<>( currentCteStatement.getCycleColumns().size() << 1 );
+		final List<SqlAstNode> arguments = new ArrayList<>( currentCteStatement.getCycleColumns().size() << 2 );
 		final Expression nullSeparator = createNullSeparator();
 
 		if ( isInRecursiveQueryPart() ) {
@@ -2512,6 +2512,7 @@ public abstract class AbstractSqlAstTranslator<T extends JdbcOperation> implemen
 						.indexOf( cycleColumn );
 				final Expression selectionExpression = selectClause.getSqlSelections().get( selectionIndex )
 						.getExpression();
+				arguments.add( nullSeparator );
 				arguments.add(
 						new SelfRenderingFunctionSqlAstExpression(
 								"coalesce",
@@ -2564,6 +2565,7 @@ public abstract class AbstractSqlAstTranslator<T extends JdbcOperation> implemen
 						.indexOf( cycleColumn );
 				final Expression selectionExpression = selectClause.getSqlSelections().get( selectionIndex )
 						.getExpression();
+				arguments.add( nullSeparator );
 				arguments.add(
 						new SelfRenderingFunctionSqlAstExpression(
 								"coalesce",

hibernate-core/src/test/java/org/hibernate/orm/test/query/CteCycleTests.java

@@ -0,0 +1,112 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.orm.test.query;
+
+import java.time.LocalDate;
+import java.util.List;
+
+import org.hibernate.query.spi.QueryImplementor;
+
+import org.hibernate.testing.orm.domain.StandardDomainModel;
+import org.hibernate.testing.orm.domain.contacts.Address;
+import org.hibernate.testing.orm.domain.contacts.Contact;
+import org.hibernate.testing.orm.junit.DialectFeatureChecks;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.JiraKey;
+import org.hibernate.testing.orm.junit.RequiresDialectFeature;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import jakarta.persistence.Tuple;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * @author Christian Beikov
+ */
+@DomainModel(standardModels = StandardDomainModel.CONTACTS)
+@SessionFactory
+public class CteCycleTests {
+
+	@Test
+	@JiraKey( "HHH-16465" )
+	@RequiresDialectFeature(feature = DialectFeatureChecks.SupportsRecursiveCtes.class)
+	public void testRecursiveCycleClause(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					final QueryImplementor<Tuple> query = session.createQuery(
+							"with alternativeContacts as (" +
+									"select c.alternativeContact alt from Contact c where c.id = :param " +
+									"union all " +
+									"select c.alt.alternativeContact alt from alternativeContacts c" +
+									")" +
+									"cycle alt set isCycle to true default false " +
+									"select ac, c.isCycle from alternativeContacts c join c.alt ac order by ac.id, c.isCycle",
+							Tuple.class
+					);
+					List<Tuple> list = query.setParameter( "param", 1 ).getResultList();
+					assertEquals( 4, list.size() );
+					assertEquals( "John", list.get( 0 ).get( 0, Contact.class ).getName().getFirst() );
+					assertEquals( "Jane", list.get( 1 ).get( 0, Contact.class ).getName().getFirst() );
+					assertFalse( list.get( 1 ).get( 1, Boolean.class ) );
+					assertEquals( "Jane", list.get( 2 ).get( 0, Contact.class ).getName().getFirst() );
+					assertTrue( list.get( 2 ).get( 1, Boolean.class ) );
+					assertEquals( "Granny", list.get( 3 ).get( 0, Contact.class ).getName().getFirst() );
+				}
+		);
+	}
+
+	@BeforeEach
+	public void prepareTestData(SessionFactoryScope scope) {
+		scope.inTransaction( (session) -> {
+			final Contact contact = new Contact(
+					1,
+					new Contact.Name( "John", "Doe" ),
+					Contact.Gender.MALE,
+					LocalDate.of( 1970, 1, 1 )
+			);
+			final Contact alternativeContact = new Contact(
+					11,
+					new Contact.Name( "Jane", "Doe" ),
+					Contact.Gender.FEMALE,
+					LocalDate.of( 1970, 1, 1 )
+			);
+			final Contact alternativeContact2 = new Contact(
+					111,
+					new Contact.Name( "Granny", "Doe" ),
+					Contact.Gender.FEMALE,
+					LocalDate.of( 1970, 1, 1 )
+			);
+			alternativeContact.setAlternativeContact( alternativeContact2 );
+			contact.setAlternativeContact( alternativeContact );
+			contact.setAddresses(
+					List.of(
+							new Address( "Street 1", 1234 ),
+							new Address( "Street 2", 5678 )
+					)
+			);
+			session.persist( alternativeContact2 );
+			session.persist( alternativeContact );
+			session.persist( contact );
+			alternativeContact2.setAlternativeContact( contact );
+
+		} );
+	}
+
+	@AfterEach
+	public void dropTestData(SessionFactoryScope scope) {
+		scope.inTransaction( (session) -> {
+			session.createMutationQuery( "update Contact set alternativeContact = null" ).executeUpdate();
+			session.createMutationQuery( "delete Contact" ).executeUpdate();
+		} );
+	}
+}