HHH-15766 Add test for issue

hibernate-core/src/test/java/org/hibernate/orm/test/query/hql/HqlUnionTest.java

@@ -0,0 +1,126 @@
+package org.hibernate.orm.test.query.hql;
+
+import java.util.List;
+
+import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+
+@DomainModel(
+		annotatedClasses = {
+				HqlUnionTest.Person.class,
+				HqlUnionTest.Dog.class,
+		}
+)
+@SessionFactory
+@TestForIssue(jiraKey = "HHH-15766")
+public class HqlUnionTest {
+
+	@BeforeAll
+	public void setUp(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					Person p = new Person( 1L, "Fabio" );
+					Person p2 = new Person( 2L, "Luisa" );
+					Dog d = new Dog( 1L, "Pluto" );
+
+					session.persist( p );
+					session.persist( p2 );
+					session.persist( d );
+				}
+		);
+	}
+
+	@Test
+	public void testUnionQueryWithOrderBy(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					List<String> results = session.createQuery(
+							"(select p.name as name from Person p order by p.id) union all (select d.name as name from Dog d order by d.id) ",
+							String.class
+					).list();
+					assertThat( results.size() ).isEqualTo( 3 );
+				}
+		);
+	}
+
+	@Test
+	public void testUnionQueryWithOrderBy2(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					List<String> results = session.createQuery(
+							"select p.name as name from Person p order by p.id union all select d.name as name from Dog d order by d.id ",
+							String.class
+					).list();
+					assertThat( results.size() ).isEqualTo( 3 );
+				}
+		);
+	}
+
+	@Test
+	public void testUnionQuery(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					List<String> results = session.createQuery(
+							"select p.name as name from Person p union all (select d.name as name from Dog d order by d.id) ",
+							String.class
+					).list();
+					assertThat( results.size() ).isEqualTo( 3 );
+				}
+		);
+	}
+
+	@Test
+	public void testUnionQuery2(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					List<String> results = session.createQuery(
+							"select p.name as name from Person p union all select d.name as name from Dog d ",
+							String.class
+					).list();
+					assertThat( results.size() ).isEqualTo( 3 );
+				}
+		);
+	}
+
+
+	@Entity(name = "Person")
+	public static class Person {
+		@Id
+		private Long id;
+
+		private String name;
+
+		public Person() {
+		}
+
+		public Person(Long id, String name) {
+			this.id = id;
+			this.name = name;
+		}
+	}
+
+	@Entity(name = "Dog")
+	public static class Dog {
+		@Id
+		private Long id;
+
+		private String name;
+
+		public Dog() {
+		}
+
+		public Dog(Long id, String name) {
+			this.id = id;
+			this.name = name;
+		}
+	}
+}