HHH-10648 : No MultipleBagFetchException is thrown when fetching two bags eagerly

hibernate-core/src/main/java/org/hibernate/loader/MultipleBagFetchException.java

@@ -19,7 +19,7 @@ public class MultipleBagFetchException extends HibernateException {
 	private final List bagRoles;
 
 	public MultipleBagFetchException(List bagRoles) {
-		super( "cannot simultaneously fetch multiple bags" );
+		super( "cannot simultaneously fetch multiple bags: " + bagRoles );
 		this.bagRoles = bagRoles;
 	}
 

hibernate-core/src/main/java/org/hibernate/loader/plan/exec/internal/AbstractLoadQueryDetails.java

@@ -10,6 +10,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.loader.MultipleBagFetchException;
 import org.hibernate.loader.plan.build.spi.LoadPlanTreePrinter;
 import org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl;
 import org.hibernate.loader.plan.exec.process.spi.CollectionReferenceInitializer;
@@ -20,6 +21,7 @@ import org.hibernate.loader.plan.exec.query.internal.SelectStatementBuilder;
 import org.hibernate.loader.plan.exec.query.spi.QueryBuildingParameters;
 import org.hibernate.loader.plan.exec.spi.AliasResolutionContext;
 import org.hibernate.loader.plan.exec.spi.LoadQueryDetails;
+import org.hibernate.loader.plan.spi.CollectionAttributeFetch;
 import org.hibernate.loader.plan.spi.CollectionReturn;
 import org.hibernate.loader.plan.spi.FetchSource;
 import org.hibernate.loader.plan.spi.LoadPlan;
@@ -168,6 +170,14 @@ public abstract class AbstractLoadQueryDetails implements LoadQueryDetails {
 			// TODO: what about index???
 		}
 
+		if ( fetchStats != null && fetchStats.getJoinedBagAttributeFetches().size() > 1 ) {
+			final List<String> bagRoles = new ArrayList<>();
+			for ( CollectionAttributeFetch bagFetch : fetchStats.getJoinedBagAttributeFetches() ) {
+				bagRoles.add( bagFetch.getCollectionPersister().getRole() );
+			}
+			throw new MultipleBagFetchException( bagRoles );
+		}
+
 		LoadPlanTreePrinter.INSTANCE.logTree( loadPlan, queryProcessor.getAliasResolutionContext() );
 
 		this.sqlStatement = select.toStatementString();

hibernate-core/src/main/java/org/hibernate/loader/plan/exec/internal/FetchStats.java

@@ -6,6 +6,10 @@
  */
 package org.hibernate.loader.plan.exec.internal;
 
+import java.util.Set;
+
+import org.hibernate.loader.plan.spi.CollectionAttributeFetch;
+
 /**
  * Contract used to report collected information about fetches.  For now that is only whether there were
  * subselect fetches found
@@ -19,4 +23,11 @@ public interface FetchStats {
 	 * @return {@code true} if subselect fetches were encountered; {@code false} otherwise.
 	 */
 	public boolean hasSubselectFetches();
+
+	/**
+	 * Returns a set of bag attributes that are join-fetched.
+	 *
+	 * @return a set of bag attributes that are join-fetched.
+	 */
+	public Set<CollectionAttributeFetch> getJoinedBagAttributeFetches();
 }

hibernate-core/src/main/java/org/hibernate/loader/plan/exec/internal/LoadQueryJoinAndFetchProcessor.java

@@ -6,6 +6,10 @@
  */
 package org.hibernate.loader.plan.exec.internal;
 
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+
 import org.hibernate.AssertionFailure;
 import org.hibernate.engine.FetchStyle;
 import org.hibernate.engine.FetchTiming;
@@ -41,6 +45,7 @@ import org.hibernate.persister.walking.internal.FetchStrategyHelper;
 import org.hibernate.sql.JoinFragment;
 import org.hibernate.sql.JoinType;
 import org.hibernate.type.AssociationType;
+import org.hibernate.type.BagType;
 import org.hibernate.type.Type;
 
 import org.jboss.logging.Logger;
@@ -657,6 +662,7 @@ public class LoadQueryJoinAndFetchProcessor {
 	 */
 	private static class FetchStatsImpl implements FetchStats {
 		private boolean hasSubselectFetch;
+		private Set<CollectionAttributeFetch> joinedBagAttributeFetches;
 
 		public void processingFetch(Fetch fetch) {
 			if ( ! hasSubselectFetch ) {
@@ -665,12 +671,32 @@ public class LoadQueryJoinAndFetchProcessor {
 					hasSubselectFetch = true;
 				}
 			}
+			if ( isJoinFetchedBag( fetch ) ) {
+				if ( joinedBagAttributeFetches == null ) {
+					joinedBagAttributeFetches = new HashSet<>();
+				}
+				joinedBagAttributeFetches.add( (CollectionAttributeFetch) fetch );
+			}
 		}
 
 		@Override
 		public boolean hasSubselectFetches() {
 			return hasSubselectFetch;
 		}
+
+		@Override
+		public Set<CollectionAttributeFetch> getJoinedBagAttributeFetches() {
+			return joinedBagAttributeFetches == null ? Collections.emptySet() : joinedBagAttributeFetches;
+		}
+
+		private boolean isJoinFetchedBag(Fetch fetch) {
+			if ( FetchStrategyHelper.isJoinFetched( fetch.getFetchStrategy() ) &&
+					CollectionAttributeFetch.class.isInstance( fetch ) ) {
+				final CollectionAttributeFetch collectionAttributeFetch = (CollectionAttributeFetch) fetch;
+				return collectionAttributeFetch.getFetchedType().getClass().isAssignableFrom( BagType.class );
+			}
+			return false;
+		}
 	}
 
 }

hibernate-core/src/test/java/org/hibernate/test/collection/bag/MultipleBagFetchHqlTest.java

@@ -0,0 +1,195 @@
+/*
+ * 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.test.collection.bag;
+
+import java.util.ArrayList;
+import java.util.List;
+import javax.persistence.Entity;
+import javax.persistence.FetchType;
+import javax.persistence.Id;
+import javax.persistence.JoinColumn;
+import javax.persistence.JoinTable;
+import javax.persistence.ManyToMany;
+import javax.persistence.OneToMany;
+import javax.persistence.Table;
+
+import org.junit.Test;
+
+import org.hibernate.Session;
+import org.hibernate.Transaction;
+import org.hibernate.loader.MultipleBagFetchException;
+import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+public class MultipleBagFetchHqlTest extends BaseCoreFunctionalTestCase {
+
+	@Override
+	protected Class[] getAnnotatedClasses() {
+		return new Class[] {
+				Post.class,
+				PostComment.class,
+				Tag.class
+		};
+	}
+
+	@Test
+	public void testMultipleBagFetchHql() throws Exception {
+
+		Session session = openSession();
+		Transaction transaction = session.beginTransaction();
+
+		Post post = new Post();
+		post.setId( 1L );
+		post.setTitle( String.format( "Post nr. %d", 1 ) );
+		PostComment comment = new PostComment();
+		comment.setId(1L);
+		comment.setReview( "Excellent!" );
+		session.persist(post);
+		session.persist( comment );
+		post.comments.add( comment );
+
+		transaction.commit();
+		session.close();
+
+
+		session = openSession();
+		session.beginTransaction();
+
+		try {
+			post = (Post) session.createQuery(
+					"select p " +
+							"from Post p " +
+							"join fetch p.tags " +
+							"join fetch p.comments " +
+							"where p.id = :id"
+			)
+					.setParameter( "id", 1L )
+					.uniqueResult();
+			fail("Should throw org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags");
+		}
+		catch ( IllegalArgumentException expected ) {
+			session.getTransaction().rollback();
+			// MultipleBagFetchException was converted to IllegalArgumentException
+			assertTrue( MultipleBagFetchException.class.isInstance( expected.getCause() ) );
+		}
+		finally {
+			session.close();
+		}
+	}
+
+	@Entity(name = "Post")
+	@Table(name = "post")
+	public static class Post {
+
+		@Id
+		private Long id;
+
+		private String title;
+
+		@OneToMany(fetch = FetchType.LAZY)
+		private List<PostComment> comments = new ArrayList<PostComment>();
+
+		@ManyToMany(fetch = FetchType.LAZY)
+		@JoinTable(name = "post_tag",
+				joinColumns = @JoinColumn(name = "post_id"),
+				inverseJoinColumns = @JoinColumn(name = "tag_id")
+		)
+		private List<Tag> tags = new ArrayList<Tag>();
+
+		public Post() {
+		}
+
+		public Post(Long id) {
+			this.id = id;
+		}
+
+		public Post(String title) {
+			this.title = title;
+		}
+
+		public Long getId() {
+			return id;
+		}
+
+		public void setId(Long id) {
+			this.id = id;
+		}
+
+		public String getTitle() {
+			return title;
+		}
+
+		public void setTitle(String title) {
+			this.title = title;
+		}
+
+		public List<Tag> getTags() {
+			return tags;
+		}
+	}
+
+	@Entity(name = "PostComment")
+	@Table(name = "post_comment")
+	public static class PostComment {
+
+		@Id
+		private Long id;
+
+		private String review;
+
+		public PostComment() {
+		}
+
+		public PostComment(String review) {
+			this.review = review;
+		}
+
+		public Long getId() {
+			return id;
+		}
+
+		public void setId(Long id) {
+			this.id = id;
+		}
+
+		public String getReview() {
+			return review;
+		}
+
+		public void setReview(String review) {
+			this.review = review;
+		}
+	}
+
+	@Entity(name = "Tag")
+	@Table(name = "tag")
+	public static class Tag {
+
+		@Id
+		private Long id;
+
+		private String name;
+
+		public Long getId() {
+			return id;
+		}
+
+		public void setId(Long id) {
+			this.id = id;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+	}
+}

hibernate-core/src/test/java/org/hibernate/test/collection/bag/MultipleBagFetchTest.java

@@ -0,0 +1,160 @@
+/*
+ * 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.test.collection.bag;
+
+import java.util.ArrayList;
+import java.util.List;
+import javax.persistence.Entity;
+import javax.persistence.FetchType;
+import javax.persistence.Id;
+import javax.persistence.JoinColumn;
+import javax.persistence.JoinTable;
+import javax.persistence.ManyToMany;
+import javax.persistence.OneToMany;
+import javax.persistence.Table;
+
+import org.hibernate.boot.Metadata;
+import org.hibernate.boot.MetadataSources;
+import org.hibernate.boot.registry.StandardServiceRegistry;
+import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+
+import org.hibernate.loader.MultipleBagFetchException;
+
+import org.junit.Test;
+
+import static org.junit.Assert.fail;
+
+public class MultipleBagFetchTest {
+
+	@Test
+	public void testEntityWithMultipleJoinFetchedBags() {
+		StandardServiceRegistry standardRegistry = new StandardServiceRegistryBuilder().build();
+
+		Metadata metadata = new MetadataSources( standardRegistry )
+				.addAnnotatedClass( Post.class )
+				.addAnnotatedClass( PostComment.class )
+				.addAnnotatedClass( Tag.class )
+				.getMetadataBuilder()
+				.build();
+		try {
+			metadata.buildSessionFactory();
+			fail( "MultipleBagFetchException should have been thrown." );
+		}
+		catch (MultipleBagFetchException expected) {
+		}
+	}
+
+	@Entity(name = "Post")
+	@Table(name = "post")
+	public static class Post {
+
+		@Id
+		private Long id;
+
+		private String title;
+
+		@OneToMany(fetch = FetchType.EAGER)
+		private List<PostComment> comments = new ArrayList<PostComment>();
+
+		@ManyToMany(fetch = FetchType.EAGER)
+		@JoinTable(name = "post_tag",
+				joinColumns = @JoinColumn(name = "post_id"),
+				inverseJoinColumns = @JoinColumn(name = "tag_id")
+		)
+		private List<Tag> tags = new ArrayList<Tag>();
+
+		public Post() {
+		}
+
+		public Post(Long id) {
+			this.id = id;
+		}
+
+		public Post(String title) {
+			this.title = title;
+		}
+
+		public Long getId() {
+			return id;
+		}
+
+		public void setId(Long id) {
+			this.id = id;
+		}
+
+		public String getTitle() {
+			return title;
+		}
+
+		public void setTitle(String title) {
+			this.title = title;
+		}
+
+		public List<Tag> getTags() {
+			return tags;
+		}
+	}
+
+	@Entity(name = "PostComment")
+	@Table(name = "post_comment")
+	public static class PostComment {
+
+		@Id
+		private Long id;
+
+		private String review;
+
+		public PostComment() {
+		}
+
+		public PostComment(String review) {
+			this.review = review;
+		}
+
+		public Long getId() {
+			return id;
+		}
+
+		public void setId(Long id) {
+			this.id = id;
+		}
+
+		public String getReview() {
+			return review;
+		}
+
+		public void setReview(String review) {
+			this.review = review;
+		}
+	}
+
+	@Entity(name = "Tag")
+	@Table(name = "tag")
+	public static class Tag {
+
+		@Id
+		private Long id;
+
+		private String name;
+
+		public Long getId() {
+			return id;
+		}
+
+		public void setId(Long id) {
+			this.id = id;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+	}
+}