HHH-16565 Add test for issue

hibernate-core/src/test/java/org/hibernate/orm/test/cache/polymorphism/PolymorphicCacheAndBatchingTest.java

@@ -0,0 +1,65 @@
+/*
+ * 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.cache.polymorphism;
+
+import java.util.List;
+
+import org.hibernate.CacheMode;
+import org.hibernate.cache.spi.CacheImplementor;
+import org.hibernate.cfg.AvailableSettings;
+
+import org.hibernate.testing.orm.junit.Jira;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.hibernate.testing.orm.junit.Setting;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Note: when batch fetching a single id this might not happen since in some cases
+ * we use a single ID entity loader that does not read the result from the PC but
+ * directly from the result of the query.
+ * <p>
+ * With multi-load, however, the problem is always apparent.
+ *
+ * @author Marco Belladelli
+ */
+@ServiceRegistry( settings = @Setting( name = AvailableSettings.DEFAULT_BATCH_FETCH_SIZE, value = "10" ) )
+@Jira( "https://hibernate.atlassian.net/browse/HHH-16565" )
+public class PolymorphicCacheAndBatchingTest extends PolymorphicCacheTest {
+	@Test
+	public void testMultiLoad(SessionFactoryScope scope) {
+		final CacheImplementor cache = scope.getSessionFactory().getCache();
+
+		assertThat( cache.containsEntity( CachedItem1.class, 1 ) ).isTrue();
+		assertThat( cache.containsEntity( CachedItem2.class, 2 ) ).isTrue();
+
+		// test accessing the wrong class by id with a cache-hit
+		scope.inTransaction( session -> {
+			final List<CachedItem2> resultList = session.byMultipleIds( CachedItem2.class )
+					.with( CacheMode.NORMAL )
+					.enableSessionCheck( true )
+					.multiLoad( 1, 2 );
+			assertThat( resultList ).hasSize( 2 );
+			assertThat( resultList.get( 0 ) ).isNull();
+			assertThat( resultList.get( 1 ).getName() ).isEqualTo( "name 2" );
+		} );
+
+		// test accessing the wrong class by id with no cache-hit
+		cache.evictEntityData();
+		scope.inTransaction( (session) -> {
+			final List<CachedItem2> resultList = session.byMultipleIds( CachedItem2.class )
+					.with( CacheMode.NORMAL )
+					.enableSessionCheck( true )
+					.multiLoad( 1, 2 );
+			assertThat( resultList ).hasSize( 2 );
+			assertThat( resultList.get( 0 ) ).isNull();
+			assertThat( resultList.get( 1 ).getName() ).isEqualTo( "name 2" );
+		} );
+	}
+}