Throw MultipleBagFetchException when trying to fetch multiple bags

hibernate-core/src/main/java/org/hibernate/collection/internal/AbstractBagSemantics.java

@@ -12,15 +12,14 @@ import java.util.Iterator;
 import java.util.function.Consumer;
 
 import org.hibernate.LockMode;
+import org.hibernate.collection.spi.BagSemantics;
 import org.hibernate.collection.spi.CollectionInitializerProducer;
-import org.hibernate.collection.spi.CollectionSemantics;
 import org.hibernate.engine.FetchTiming;
 import org.hibernate.internal.util.collections.CollectionHelper;
 import org.hibernate.metamodel.mapping.CollectionPart;
 import org.hibernate.metamodel.mapping.PluralAttributeMapping;
 import org.hibernate.persister.collection.CollectionPersister;
 import org.hibernate.query.NavigablePath;
-import org.hibernate.sql.ast.tree.from.TableGroup;
 import org.hibernate.sql.results.graph.Fetch;
 import org.hibernate.sql.results.graph.collection.internal.BagInitializerProducer;
 import org.hibernate.sql.results.graph.DomainResultCreationState;
@@ -29,7 +28,7 @@ import org.hibernate.sql.results.graph.FetchParent;
 /**
  * @author Steve Ebersole
  */
-public abstract class AbstractBagSemantics<B extends Collection<?>> implements CollectionSemantics<B> {
+public abstract class AbstractBagSemantics<B extends Collection<?>> implements BagSemantics<B> {
 	@Override
 	public Class<B> getCollectionJavaType() {
 		//noinspection unchecked

hibernate-core/src/main/java/org/hibernate/collection/spi/BagSemantics.java

@@ -0,0 +1,14 @@
+/*
+ * 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.collection.spi;
+
+/**
+ * @author Andrea Boriero
+ */
+public interface BagSemantics<B> extends CollectionSemantics<B> {
+}
+

hibernate-core/src/main/java/org/hibernate/loader/ast/internal/LoaderSelectBuilder.java

@@ -16,6 +16,7 @@ import java.util.function.Consumer;
 
 import org.hibernate.LockMode;
 import org.hibernate.LockOptions;
+import org.hibernate.collection.spi.BagSemantics;
 import org.hibernate.engine.FetchStyle;
 import org.hibernate.engine.FetchTiming;
 import org.hibernate.engine.profile.FetchProfile;
@@ -27,6 +28,7 @@ import org.hibernate.graph.GraphSemantic;
 import org.hibernate.graph.spi.RootGraphImplementor;
 import org.hibernate.internal.FilterHelper;
 import org.hibernate.internal.util.MutableInteger;
+import org.hibernate.loader.MultipleBagFetchException;
 import org.hibernate.loader.ast.spi.Loadable;
 import org.hibernate.loader.ast.spi.Loader;
 import org.hibernate.metamodel.mapping.BasicValuedModelPart;
@@ -43,6 +45,7 @@ import org.hibernate.metamodel.mapping.ordering.OrderByFragment;
 import org.hibernate.persister.collection.CollectionPersister;
 import org.hibernate.persister.entity.Joinable;
 import org.hibernate.query.ComparisonOperator;
+import org.hibernate.query.EntityIdentifierNavigablePath;
 import org.hibernate.query.NavigablePath;
 import org.hibernate.sql.ast.spi.SimpleFromClauseAccessImpl;
 import org.hibernate.sql.ast.spi.SqlAliasBaseManager;
@@ -443,7 +446,8 @@ public class LoaderSelectBuilder {
 		}
 
 		final List<Fetch> fetches = new ArrayList<>();
-		final BiConsumer<Fetchable, Boolean> processor = createFetchableBiConsumer( fetchParent, querySpec, creationState, fetches );
+		final List<String> bagRoles = new ArrayList<>();
+		final BiConsumer<Fetchable, Boolean> processor = createFetchableBiConsumer( fetchParent, querySpec, creationState, fetches, bagRoles );
 
 		final FetchableContainer referencedMappingContainer = fetchParent.getReferencedMappingContainer();
 		if ( fetchParent.getNavigablePath().getParent() != null ) {
@@ -452,6 +456,9 @@ public class LoaderSelectBuilder {
 		}
 		referencedMappingContainer.visitFetchables(
 				fetchable -> processor.accept( fetchable, false ), null );
+		if ( bagRoles.size() > 1 ) {
+			throw new MultipleBagFetchException( bagRoles );
+		}
 		return fetches;
 	}
 
@@ -459,11 +466,12 @@ public class LoaderSelectBuilder {
 			FetchParent fetchParent,
 			QuerySpec querySpec,
 			LoaderSqlAstCreationState creationState,
-			List<Fetch> fetches) {
+			List<Fetch> fetches,
+			List<String> bagRoles) {
 		return (fetchable, isKeyFetchable) -> {
 			NavigablePath panrentNavigablePath = fetchParent.getNavigablePath();
 			if ( isKeyFetchable ) {
-				panrentNavigablePath = panrentNavigablePath.append( EntityIdentifierMapping.ROLE_LOCAL_NAME );
+				panrentNavigablePath = new EntityIdentifierNavigablePath( panrentNavigablePath );
 			}
 			final NavigablePath fetchablePath = panrentNavigablePath.append( fetchable.getFetchableName() );
 
@@ -542,23 +550,31 @@ public class LoaderSelectBuilder {
 						null,
 						creationState
 				);
-				fetches.add( fetch );
 
-				if ( fetchable instanceof PluralAttributeMapping && fetchTiming == FetchTiming.IMMEDIATE && joined ) {
-					final TableGroup joinTableGroup = creationState.getFromClauseAccess().getTableGroup( fetchablePath );
+				if ( fetch.getTiming() == FetchTiming.IMMEDIATE && fetchable instanceof PluralAttributeMapping ) {
 					final PluralAttributeMapping pluralAttributeMapping = (PluralAttributeMapping) fetchable;
-					applyFiltering(
-							querySpec,
-							joinTableGroup,
-							pluralAttributeMapping
-					);
-					applyOrdering(
-							querySpec,
-							fetchablePath,
-							pluralAttributeMapping,
-							creationState
-					);
+					if ( pluralAttributeMapping.getMappedTypeDescriptor()
+							.getCollectionSemantics() instanceof BagSemantics ) {
+						bagRoles.add( fetchable.getNavigableRole().getNavigableName() );
+					}
+					if ( joined ) {
+						final TableGroup joinTableGroup = creationState.getFromClauseAccess()
+								.getTableGroup( fetchablePath );
+						applyFiltering(
+								querySpec,
+								joinTableGroup,
+								pluralAttributeMapping
+						);
+						applyOrdering(
+								querySpec,
+								fetchablePath,
+								pluralAttributeMapping,
+								creationState
+						);
+					}
 				}
+
+				fetches.add( fetch );
 			}
 			finally {
 				if ( changeFetchDepth ) {

hibernate-core/src/main/java/org/hibernate/loader/ast/internal/SingleIdEntityLoaderStandardImpl.java

@@ -48,7 +48,16 @@ public class SingleIdEntityLoaderStandardImpl<T> extends SingleIdEntityLoaderSup
 	public void prepare() {
 		// see `org.hibernate.persister.entity.AbstractEntityPersister#createLoaders`
 		//		we should pre-load a few - maybe LockMode.NONE and LockMode.READ
-
+		final LockOptions lockOptions = LockOptions.NONE;
+		final LoadQueryInfluencers queryInfluencers = new LoadQueryInfluencers( sessionFactory );
+		final SingleIdLoadPlan<T> plan = createLoadPlan(
+				lockOptions,
+				queryInfluencers,
+				sessionFactory
+		);
+		if ( determineIfReusable( lockOptions, queryInfluencers ) ) {
+			selectByLockMode.put( lockOptions.getLockMode(), plan );
+		}
 	}
 
 	@Override

hibernate-core/src/main/java/org/hibernate/loader/ast/internal/SingleIdEntityLoaderSupport.java

@@ -16,7 +16,7 @@ import org.hibernate.metamodel.mapping.EntityMappingType;
  */
 public abstract class SingleIdEntityLoaderSupport<T> implements SingleIdEntityLoader<T> {
 	private final EntityMappingType entityDescriptor;
-	private final SessionFactoryImplementor sessionFactory;
+	protected final SessionFactoryImplementor sessionFactory;
 
 	private DatabaseSnapshotExecutor databaseSnapshotExecutor;
 

hibernate-core/src/main/java/org/hibernate/metamodel/internal/AbstractCompositeIdentifierMapping.java

@@ -0,0 +1,242 @@
+/*
+ * 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.metamodel.internal;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.function.Consumer;
+
+import org.hibernate.LockMode;
+import org.hibernate.engine.FetchStyle;
+import org.hibernate.engine.FetchTiming;
+import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.metamodel.mapping.ColumnConsumer;
+import org.hibernate.metamodel.mapping.CompositeIdentifierMapping;
+import org.hibernate.metamodel.mapping.EmbeddableMappingType;
+import org.hibernate.metamodel.mapping.EntityIdentifierMapping;
+import org.hibernate.metamodel.mapping.EntityMappingType;
+import org.hibernate.metamodel.mapping.JdbcMapping;
+import org.hibernate.metamodel.mapping.ModelPart;
+import org.hibernate.metamodel.mapping.SingularAttributeMapping;
+import org.hibernate.metamodel.mapping.StateArrayContributorMetadataAccess;
+import org.hibernate.metamodel.mapping.internal.ToOneAttributeMapping;
+import org.hibernate.metamodel.model.domain.NavigableRole;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.ast.Clause;
+import org.hibernate.sql.ast.SqlAstJoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBaseGenerator;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
+import org.hibernate.sql.ast.spi.SqlExpressionResolver;
+import org.hibernate.sql.ast.tree.from.CompositeTableGroup;
+import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.ast.tree.from.TableGroupJoin;
+import org.hibernate.sql.results.graph.DomainResult;
+import org.hibernate.sql.results.graph.DomainResultCreationState;
+import org.hibernate.sql.results.graph.Fetch;
+import org.hibernate.sql.results.graph.FetchOptions;
+import org.hibernate.sql.results.graph.FetchParent;
+import org.hibernate.sql.results.graph.embeddable.EmbeddableValuedFetchable;
+import org.hibernate.sql.results.graph.embeddable.internal.EmbeddableFetchImpl;
+import org.hibernate.sql.results.graph.embeddable.internal.EmbeddableResultImpl;
+import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
+import org.hibernate.type.spi.TypeConfiguration;
+
+/**
+ * @author Andrea Boriero
+ */
+public abstract class AbstractCompositeIdentifierMapping
+		implements CompositeIdentifierMapping, EmbeddableValuedFetchable, FetchOptions {
+	private final NavigableRole navigableRole;
+	private final String tableExpression;
+
+	private final StateArrayContributorMetadataAccess attributeMetadataAccess;
+	private final List<String> columnNames;
+
+	private final EntityMappingType entityMapping;
+	private final EmbeddableMappingType embeddableDescriptor;
+
+	private final SessionFactoryImplementor sessionFactory;
+
+	public AbstractCompositeIdentifierMapping(
+			StateArrayContributorMetadataAccess attributeMetadataAccess,
+			EmbeddableMappingType embeddableDescriptor,
+			EntityMappingType entityMapping,
+			String tableExpression,
+			String[] columnNames,
+			SessionFactoryImplementor sessionFactory) {
+		this.attributeMetadataAccess = attributeMetadataAccess;
+		this.embeddableDescriptor = embeddableDescriptor;
+		this.entityMapping = entityMapping;
+		this.tableExpression = tableExpression;
+		this.sessionFactory = sessionFactory;
+
+		this.columnNames = Arrays.asList( columnNames );
+
+		this.navigableRole = entityMapping.getNavigableRole()
+				.appendContainer( EntityIdentifierMapping.ROLE_LOCAL_NAME );
+	}
+
+	@Override
+	public EmbeddableMappingType getMappedTypeDescriptor() {
+		return embeddableDescriptor;
+	}
+
+	@Override
+	public EmbeddableMappingType getPartMappingType() {
+		return getEmbeddableTypeDescriptor();
+	}
+
+	@Override
+	public JavaTypeDescriptor getJavaTypeDescriptor() {
+		return getEmbeddableTypeDescriptor().getMappedJavaTypeDescriptor();
+	}
+
+	@Override
+	public EmbeddableMappingType getEmbeddableTypeDescriptor() {
+		return embeddableDescriptor;
+	}
+
+	@Override
+	public String getContainingTableExpression() {
+		return tableExpression;
+	}
+
+	@Override
+	public NavigableRole getNavigableRole() {
+		return navigableRole;
+	}
+
+	@Override
+	public List<String> getMappedColumnExpressions() {
+		return columnNames;
+	}
+
+	@Override
+	public void visitColumns(ColumnConsumer consumer) {
+		getAttributes().forEach(
+				attribute -> {
+					if ( attribute instanceof ToOneAttributeMapping ) {
+						final ToOneAttributeMapping associationAttributeMapping = (ToOneAttributeMapping) attribute;
+						associationAttributeMapping.getForeignKeyDescriptor().visitReferringColumns( consumer );
+					}
+					else {
+						attribute.visitColumns( consumer );
+					}
+				}
+		);
+	}
+
+	@Override
+	public Fetch generateFetch(
+			FetchParent fetchParent,
+			NavigablePath fetchablePath,
+			FetchTiming fetchTiming,
+			boolean selected,
+			LockMode lockMode,
+			String resultVariable,
+			DomainResultCreationState creationState) {
+		return new EmbeddableFetchImpl(
+				fetchablePath,
+				this,
+				fetchParent,
+				fetchTiming,
+				selected,
+				attributeMetadataAccess.resolveAttributeMetadata( null ).isNullable(),
+				creationState
+		);
+	}
+
+	@Override
+	public TableGroupJoin createTableGroupJoin(
+			NavigablePath navigablePath,
+			TableGroup lhs,
+			String explicitSourceAlias,
+			SqlAstJoinType sqlAstJoinType,
+			LockMode lockMode,
+			SqlAliasBaseGenerator aliasBaseGenerator,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext) {
+		final CompositeTableGroup compositeTableGroup = new CompositeTableGroup(
+				navigablePath,
+				this,
+				lhs
+		);
+
+		final TableGroupJoin join = new TableGroupJoin( navigablePath, SqlAstJoinType.LEFT, compositeTableGroup, null );
+		lhs.addTableGroupJoin( join );
+
+		return join;
+	}
+
+	@Override
+	public ModelPart findSubPart(String name, EntityMappingType treatTargetType) {
+		return embeddableDescriptor.findSubPart( name, treatTargetType );
+	}
+
+	@Override
+	public void visitSubParts(
+			Consumer<ModelPart> consumer,
+			EntityMappingType treatTargetType) {
+		embeddableDescriptor.visitSubParts( consumer, treatTargetType );
+	}
+
+	@Override
+	public void visitJdbcTypes(
+			Consumer<JdbcMapping> action,
+			Clause clause,
+			TypeConfiguration typeConfiguration) {
+		embeddableDescriptor.visitJdbcTypes( action, clause, typeConfiguration );
+	}
+
+	@Override
+	public <T> DomainResult<T> createDomainResult(
+			NavigablePath navigablePath,
+			TableGroup tableGroup,
+			String resultVariable,
+			DomainResultCreationState creationState) {
+		return new EmbeddableResultImpl<>(
+				navigablePath,
+				this,
+				resultVariable,
+				creationState
+		);
+	}
+
+	@Override
+	public Object instantiate() {
+		return getEntityMapping().getRepresentationStrategy().getInstantiator().instantiate( sessionFactory );
+	}
+
+	@Override
+	public SingularAttributeMapping getParentInjectionAttributeMapping() {
+		return null;
+	}
+
+	@Override
+	public EntityMappingType findContainingEntityMapping() {
+		return entityMapping;
+	}
+
+	@Override
+	public FetchOptions getMappedFetchOptions() {
+		return this;
+	}
+
+	@Override
+	public FetchStyle getStyle() {
+		return FetchStyle.JOIN;
+	}
+
+	@Override
+	public FetchTiming getTiming() {
+		return FetchTiming.IMMEDIATE;
+	}
+
+	protected EntityMappingType getEntityMapping() {
+		return entityMapping;
+	}
+}

hibernate-core/src/main/java/org/hibernate/metamodel/mapping/PluralAttributeMapping.java

@@ -28,6 +28,9 @@ public interface PluralAttributeMapping
 
 	CollectionPart getIndexDescriptor();
 
+	@Override
+	CollectionMappingType getMappedTypeDescriptor();
+
 	interface IndexMetadata {
 		CollectionPart getIndexDescriptor();
 		int getListIndexBase();

hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/BasicValuedCollectionPart.java

@@ -21,6 +21,7 @@ import org.hibernate.metamodel.mapping.MappingType;
 import org.hibernate.metamodel.model.convert.spi.BasicValueConverter;
 import org.hibernate.metamodel.model.domain.NavigableRole;
 import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.query.EntityIdentifierNavigablePath;
 import org.hibernate.query.NavigablePath;
 import org.hibernate.sql.ast.spi.SqlExpressionResolver;
 import org.hibernate.sql.ast.spi.SqlSelection;
@@ -187,9 +188,14 @@ public class BasicValuedCollectionPart
 				nature.getName()
 		);
 
+		NavigablePath parentNavigablePath = fetchablePath.getParent();
+		if ( parentNavigablePath instanceof EntityIdentifierNavigablePath ) {
+			parentNavigablePath = parentNavigablePath.getParent();
+		}
+
 		final TableGroup tableGroup = creationState.getSqlAstCreationState()
 				.getFromClauseAccess()
-				.findTableGroup( fetchablePath.getParent() );
+				.findTableGroup( parentNavigablePath );
 		final SqlSelection sqlSelection = resolveSqlSelection( tableGroup, creationState );
 
 		return new BasicFetch(

hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/EmbeddedIdentifierMappingImpl.java

@@ -6,102 +6,62 @@
  */
 package org.hibernate.metamodel.mapping.internal;
 
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 import java.util.function.Consumer;
 
-import org.hibernate.LockMode;
-import org.hibernate.engine.FetchStyle;
-import org.hibernate.engine.FetchTiming;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.internal.util.collections.CollectionHelper;
-import org.hibernate.metamodel.mapping.ColumnConsumer;
-import org.hibernate.metamodel.mapping.CompositeIdentifierMapping;
+import org.hibernate.metamodel.internal.AbstractCompositeIdentifierMapping;
 import org.hibernate.metamodel.mapping.EmbeddableMappingType;
 import org.hibernate.metamodel.mapping.EntityIdentifierMapping;
 import org.hibernate.metamodel.mapping.EntityMappingType;
 import org.hibernate.metamodel.mapping.JdbcMapping;
-import org.hibernate.metamodel.mapping.MappingType;
-import org.hibernate.metamodel.mapping.ModelPart;
 import org.hibernate.metamodel.mapping.SingularAttributeMapping;
 import org.hibernate.metamodel.mapping.StateArrayContributorMetadataAccess;
-import org.hibernate.metamodel.model.domain.NavigableRole;
 import org.hibernate.property.access.spi.PropertyAccess;
 import org.hibernate.proxy.HibernateProxy;
-import org.hibernate.query.NavigablePath;
 import org.hibernate.query.sqm.sql.SqmToSqlAstConverter;
 import org.hibernate.sql.ast.Clause;
-import org.hibernate.sql.ast.SqlAstJoinType;
-import org.hibernate.sql.ast.spi.SqlAliasBaseGenerator;
-import org.hibernate.sql.ast.spi.SqlAstCreationContext;
 import org.hibernate.sql.ast.spi.SqlAstCreationState;
 import org.hibernate.sql.ast.spi.SqlExpressionResolver;
 import org.hibernate.sql.ast.tree.expression.ColumnReference;
 import org.hibernate.sql.ast.tree.expression.Expression;
 import org.hibernate.sql.ast.tree.expression.SqlTuple;
-import org.hibernate.sql.ast.tree.from.CompositeTableGroup;
 import org.hibernate.sql.ast.tree.from.TableGroup;
-import org.hibernate.sql.ast.tree.from.TableGroupJoin;
 import org.hibernate.sql.ast.tree.from.TableReference;
-import org.hibernate.sql.results.graph.DomainResult;
-import org.hibernate.sql.results.graph.DomainResultCreationState;
-import org.hibernate.sql.results.graph.Fetch;
-import org.hibernate.sql.results.graph.FetchOptions;
-import org.hibernate.sql.results.graph.FetchParent;
-import org.hibernate.sql.results.graph.embeddable.EmbeddableValuedFetchable;
-import org.hibernate.sql.results.graph.embeddable.internal.EmbeddableFetchImpl;
-import org.hibernate.sql.results.graph.embeddable.internal.EmbeddableResultImpl;
-import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
-import org.hibernate.type.spi.TypeConfiguration;
 
 /**
  * Support for {@link javax.persistence.EmbeddedId}
  *
  * @author Andrea Boriero
  */
-public class EmbeddedIdentifierMappingImpl
-		implements CompositeIdentifierMapping, EmbeddableValuedFetchable, FetchOptions {
-	private final NavigableRole navigableRole;
-	private final EntityMappingType entityMapping;
+public class EmbeddedIdentifierMappingImpl extends AbstractCompositeIdentifierMapping {
 	private final String name;
-	private final MappingType type;
-	private final StateArrayContributorMetadataAccess attributeMetadataAccess;
 	private final PropertyAccess propertyAccess;
-	private final String tableExpression;
-	private final String[] attrColumnNames;
-	private final SessionFactoryImplementor sessionFactory;
 
 	@SuppressWarnings("WeakerAccess")
 	public EmbeddedIdentifierMappingImpl(
 			EntityMappingType entityMapping,
 			String name,
-			MappingType type,
+			EmbeddableMappingType embeddableDescriptor,
 			StateArrayContributorMetadataAccess attributeMetadataAccess,
 			PropertyAccess propertyAccess,
 			String tableExpression,
 			String[] attrColumnNames,
 			SessionFactoryImplementor sessionFactory) {
-		this.navigableRole = entityMapping.getNavigableRole().appendContainer( EntityIdentifierMapping.ROLE_LOCAL_NAME );
-		this.entityMapping = entityMapping;
+		super(
+				attributeMetadataAccess,
+				embeddableDescriptor,
+				entityMapping,
+				tableExpression,
+				attrColumnNames,
+				sessionFactory
+		);
+
 		this.name = name;
-		this.type = type;
-		this.attributeMetadataAccess = attributeMetadataAccess;
 		this.propertyAccess = propertyAccess;
-		this.tableExpression = tableExpression;
-		this.attrColumnNames = attrColumnNames;
-		this.sessionFactory = sessionFactory;
-	}
-
-	@Override
-	public EmbeddableMappingType getPartMappingType() {
-		return (EmbeddableMappingType) type;
-	}
-
-	@Override
-	public JavaTypeDescriptor getJavaTypeDescriptor() {
-		return getMappedTypeDescriptor().getMappedJavaTypeDescriptor();
 	}
 
 	@Override
@@ -109,11 +69,6 @@ public class EmbeddedIdentifierMappingImpl
 		return name;
 	}
 
-	@Override
-	public NavigableRole getNavigableRole() {
-		return navigableRole;
-	}
-
 	@Override
 	public Object getIdentifier(Object entity, SharedSessionContractImplementor session) {
 		if ( entity instanceof HibernateProxy ) {
@@ -127,44 +82,6 @@ public class EmbeddedIdentifierMappingImpl
 		propertyAccess.getSetter().set( entity, id, session.getFactory() );
 	}
 
-	@Override
-	public Object instantiate() {
-		return entityMapping.getRepresentationStrategy().getInstantiator().instantiate( sessionFactory );
-	}
-
-	@Override
-	public EmbeddableMappingType getEmbeddableTypeDescriptor() {
-		return getMappedTypeDescriptor();
-	}
-
-	@Override
-	public EmbeddableMappingType getMappedTypeDescriptor() {
-		return (EmbeddableMappingType) type;
-	}
-
-	@Override
-	public String getContainingTableExpression() {
-		return tableExpression;
-	}
-
-	@Override
-	public List<String> getMappedColumnExpressions() {
-		return Arrays.asList( attrColumnNames );
-	}
-
-	@Override
-	public SingularAttributeMapping getParentInjectionAttributeMapping() {
-		return null;
-	}
-
-	@Override
-	public void visitJdbcTypes(
-			Consumer<JdbcMapping> action,
-			Clause clause,
-			TypeConfiguration typeConfiguration) {
-		getMappedTypeDescriptor().visitJdbcTypes( action,clause,typeConfiguration );
-	}
-
 	@Override
 	public void visitJdbcValues(
 			Object value,
@@ -189,27 +106,14 @@ public class EmbeddedIdentifierMappingImpl
 		);
 	}
 
-	@Override
-	public <T> DomainResult<T> createDomainResult(
-			NavigablePath navigablePath,
-			TableGroup tableGroup,
-			String resultVariable,
-			DomainResultCreationState creationState) {
-		return new EmbeddableResultImpl<>(
-				navigablePath,
-				this,
-				resultVariable,
-				creationState
-		);
-	}
-
 	@Override
 	public Expression toSqlExpression(
 			TableGroup tableGroup,
 			Clause clause,
 			SqmToSqlAstConverter walker,
 			SqlAstCreationState sqlAstCreationState) {
-		final List<ColumnReference> columnReferences = CollectionHelper.arrayList( attrColumnNames.length );
+		final List<String> attrColumnNames = getMappedColumnExpressions();
+		final List<ColumnReference> columnReferences = CollectionHelper.arrayList( attrColumnNames.size() );
 		final TableReference tableReference = tableGroup.resolveTableReference( getContainingTableExpression() );
 		getEmbeddableTypeDescriptor().visitJdbcTypes(
 				new Consumer<JdbcMapping>() {
@@ -217,21 +121,22 @@ public class EmbeddedIdentifierMappingImpl
 
 					@Override
 					public void accept(JdbcMapping jdbcMapping) {
-						final String attrColumnExpr = attrColumnNames[ index++ ];
+						final String attrColumnExpr = attrColumnNames.get( index++ );
 
-						final Expression columnReference = sqlAstCreationState.getSqlExpressionResolver().resolveSqlExpression(
-								SqlExpressionResolver.createColumnReferenceKey(
-										tableReference,
-										attrColumnExpr
-								),
-								sqlAstProcessingState -> new ColumnReference(
-										tableReference.getIdentificationVariable(),
-										attrColumnExpr,
-										false,
-										jdbcMapping,
-										sqlAstCreationState.getCreationContext().getSessionFactory()
-								)
-						);
+						final Expression columnReference = sqlAstCreationState.getSqlExpressionResolver()
+								.resolveSqlExpression(
+										SqlExpressionResolver.createColumnReferenceKey(
+												tableReference,
+												attrColumnExpr
+										),
+										sqlAstProcessingState -> new ColumnReference(
+												tableReference.getIdentificationVariable(),
+												attrColumnExpr,
+												false,
+												jdbcMapping,
+												sqlAstCreationState.getCreationContext().getSessionFactory()
+										)
+								);
 
 						columnReferences.add( (ColumnReference) columnReference );
 					}
@@ -243,99 +148,23 @@ public class EmbeddedIdentifierMappingImpl
 		return new SqlTuple( columnReferences, this );
 	}
 
-	@Override
-	public TableGroupJoin createTableGroupJoin(
-			NavigablePath navigablePath,
-			TableGroup lhs,
-			String explicitSourceAlias,
-			SqlAstJoinType sqlAstJoinType,
-			LockMode lockMode,
-			SqlAliasBaseGenerator aliasBaseGenerator,
-			SqlExpressionResolver sqlExpressionResolver,
-			SqlAstCreationContext creationContext) {
-		final CompositeTableGroup compositeTableGroup = new CompositeTableGroup(
-				navigablePath,
-				this,
-				lhs
-		);
-
-		final TableGroupJoin join = new TableGroupJoin( navigablePath, SqlAstJoinType.LEFT, compositeTableGroup, null );
-		lhs.addTableGroupJoin( join );
-
-		return join;
-	}
-
 	@Override
 	public String getSqlAliasStem() {
-			return name;
+		return name;
 	}
 
-	@Override
-	public ModelPart findSubPart(String name, EntityMappingType treatTargetType) {
-		return getMappedTypeDescriptor().findSubPart( name, treatTargetType );
-	}
-
-	@Override
-	public void visitSubParts(
-			Consumer<ModelPart> consumer,
-			EntityMappingType treatTargetType) {
-		getMappedTypeDescriptor().visitSubParts( consumer, treatTargetType );
-	}
 
 	@Override
 	public String getFetchableName() {
 		return name;
 	}
 
-	@Override
-	public FetchOptions getMappedFetchOptions() {
-		return this;
-	}
-
-	@Override
-	public Fetch generateFetch(
-			FetchParent fetchParent,
-			NavigablePath fetchablePath,
-			FetchTiming fetchTiming,
-			boolean selected,
-			LockMode lockMode,
-			String resultVariable,
-			DomainResultCreationState creationState) {
-		return new EmbeddableFetchImpl(
-				fetchablePath,
-				this,
-				fetchParent,
-				fetchTiming,
-				selected,
-				attributeMetadataAccess.resolveAttributeMetadata( null ).isNullable(),
-				creationState
-		);
-	}
 
 	@Override
 	public int getNumberOfFetchables() {
 		return getEmbeddableTypeDescriptor().getNumberOfAttributeMappings();
 	}
 
-	@Override
-	public void visitColumns(ColumnConsumer consumer) {
-		getAttributes().forEach(
-				attribute -> {
-					if ( attribute instanceof ToOneAttributeMapping ) {
-						final ToOneAttributeMapping associationAttributeMapping = (ToOneAttributeMapping) attribute;
-						associationAttributeMapping.getForeignKeyDescriptor().visitReferringColumns( consumer );
-					}
-					else {
-						attribute.visitColumns( consumer );
-					}
-				}
-		);
-	}
-
-	@Override
-	public EntityMappingType findContainingEntityMapping() {
-		return entityMapping;
-	}
 
 	@Override
 	public int getAttributeCount() {
@@ -348,13 +177,4 @@ public class EmbeddedIdentifierMappingImpl
 		return (Collection) getEmbeddableTypeDescriptor().getAttributeMappings();
 	}
 
-	@Override
-	public FetchStyle getStyle() {
-		return FetchStyle.JOIN;
-	}
-
-	@Override
-	public FetchTiming getTiming() {
-		return FetchTiming.IMMEDIATE;
-	}
 }

hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/NonAggregatedIdentifierMappingImpl.java

@@ -6,67 +6,34 @@
  */
 package org.hibernate.metamodel.mapping.internal;
 
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
-import java.util.function.Consumer;
 
-import org.hibernate.LockMode;
-import org.hibernate.engine.FetchStyle;
-import org.hibernate.engine.FetchTiming;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.mapping.Component;
-import org.hibernate.metamodel.mapping.CompositeIdentifierMapping;
+import org.hibernate.metamodel.internal.AbstractCompositeIdentifierMapping;
 import org.hibernate.metamodel.mapping.EmbeddableMappingType;
-import org.hibernate.metamodel.mapping.EntityIdentifierMapping;
 import org.hibernate.metamodel.mapping.EntityMappingType;
-import org.hibernate.metamodel.mapping.ModelPart;
 import org.hibernate.metamodel.mapping.SingularAttributeMapping;
 import org.hibernate.metamodel.mapping.StateArrayContributorMetadataAccess;
-import org.hibernate.metamodel.model.domain.NavigableRole;
-import org.hibernate.query.NavigablePath;
 import org.hibernate.query.sqm.sql.SqmToSqlAstConverter;
 import org.hibernate.sql.ast.Clause;
-import org.hibernate.sql.ast.SqlAstJoinType;
-import org.hibernate.sql.ast.spi.SqlAliasBaseGenerator;
-import org.hibernate.sql.ast.spi.SqlAstCreationContext;
 import org.hibernate.sql.ast.spi.SqlAstCreationState;
-import org.hibernate.sql.ast.spi.SqlExpressionResolver;
 import org.hibernate.sql.ast.tree.expression.Expression;
-import org.hibernate.sql.ast.tree.from.CompositeTableGroup;
 import org.hibernate.sql.ast.tree.from.TableGroup;
-import org.hibernate.sql.ast.tree.from.TableGroupJoin;
-import org.hibernate.sql.results.graph.DomainResult;
-import org.hibernate.sql.results.graph.DomainResultCreationState;
-import org.hibernate.sql.results.graph.Fetch;
-import org.hibernate.sql.results.graph.FetchOptions;
-import org.hibernate.sql.results.graph.FetchParent;
-import org.hibernate.sql.results.graph.embeddable.EmbeddableValuedFetchable;
-import org.hibernate.sql.results.graph.embeddable.internal.EmbeddableFetchImpl;
-import org.hibernate.sql.results.graph.embeddable.internal.EmbeddableResultImpl;
-import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
 
 /**
  * A "non-aggregated" composite identifier.
- *
+ * <p>
  * This is an identifier mapped using JPA's {@link javax.persistence.MapsId} feature.
  *
- * @apiNote Technically a MapsId id does not have to be composite; we still handle that this class however
- *
  * @author Steve Ebersole
+ * @apiNote Technically a MapsId id does not have to be composite; we still handle that this class however
  */
-public class NonAggregatedIdentifierMappingImpl
-		implements CompositeIdentifierMapping, EmbeddableValuedFetchable, FetchOptions {
-	private final EmbeddableMappingType embeddableDescriptor;
-	private final NavigableRole navigableRole;
-	private final EntityMappingType entityMapping;
+public class NonAggregatedIdentifierMappingImpl extends AbstractCompositeIdentifierMapping {
 
 	private final List<SingularAttributeMapping> idAttributeMappings;
 
-	private final StateArrayContributorMetadataAccess attributeMetadataAccess;
-	private final String rootTableName;
-	private final List<String> idColumnNames;
-
 	public NonAggregatedIdentifierMappingImpl(
 			EmbeddableMappingType embeddableDescriptor,
 			EntityMappingType entityMapping,
@@ -78,35 +45,15 @@ public class NonAggregatedIdentifierMappingImpl
 			Component bootIdClassDescriptor,
 			MappingModelCreationProcess creationProcess) {
 		// todo (6.0) : handle MapsId and IdClass
-
-		this.embeddableDescriptor = embeddableDescriptor;
-		this.entityMapping = entityMapping;
+		super(
+				attributeMetadataAccess,
+				embeddableDescriptor,
+				entityMapping,
+				rootTableName,
+				rootTableKeyColumnNames,
+				creationProcess.getCreationContext().getSessionFactory()
+		);
 		this.idAttributeMappings = idAttributeMappings;
-		this.attributeMetadataAccess = attributeMetadataAccess;
-		this.rootTableName = rootTableName;
-		this.idColumnNames = Arrays.asList( rootTableKeyColumnNames );
-
-		this.navigableRole = entityMapping.getNavigableRole().appendContainer( EntityIdentifierMapping.ROLE_LOCAL_NAME );
-	}
-
-	@Override
-	public EntityMappingType getPartMappingType() {
-		return entityMapping;
-	}
-
-	@Override
-	public JavaTypeDescriptor getJavaTypeDescriptor() {
-		return entityMapping.getJavaTypeDescriptor();
-	}
-
-	@Override
-	public NavigableRole getNavigableRole() {
-		return navigableRole;
-	}
-
-	@Override
-	public EmbeddableMappingType getMappedTypeDescriptor() {
-		return embeddableDescriptor;
 	}
 
 	@Override
@@ -128,56 +75,9 @@ public class NonAggregatedIdentifierMappingImpl
 	public void setIdentifier(Object entity, Object id, SharedSessionContractImplementor session) {
 		// nothing to do
 	}
-
-	@Override
-	public Object instantiate() {
-		return entityMapping;
-	}
-
-	@Override
-	public <T> DomainResult<T> createDomainResult(
-			NavigablePath navigablePath,
-			TableGroup tableGroup,
-			String resultVariable,
-			DomainResultCreationState creationState) {
-		return new EmbeddableResultImpl<>(
-				navigablePath,
-				this,
-				resultVariable,
-				creationState
-		);
-	}
-
-	@Override
-	public EntityMappingType findContainingEntityMapping() {
-		return entityMapping;
-	}
-
-
 	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 	// EmbeddableValuedFetchable
 
-
-	@Override
-	public EmbeddableMappingType getEmbeddableTypeDescriptor() {
-		return getMappedTypeDescriptor();
-	}
-
-	@Override
-	public String getContainingTableExpression() {
-		return rootTableName;
-	}
-
-	@Override
-	public List<String> getMappedColumnExpressions() {
-		return idColumnNames;
-	}
-
-	@Override
-	public SingularAttributeMapping getParentInjectionAttributeMapping() {
-		return null;
-	}
-
 	@Override
 	public Expression toSqlExpression(
 			TableGroup tableGroup,
@@ -187,85 +87,19 @@ public class NonAggregatedIdentifierMappingImpl
 		return null;
 	}
 
-	@Override
-	public TableGroupJoin createTableGroupJoin(
-			NavigablePath navigablePath,
-			TableGroup lhs,
-			String explicitSourceAlias,
-			SqlAstJoinType sqlAstJoinType,
-			LockMode lockMode,
-			SqlAliasBaseGenerator aliasBaseGenerator,
-			SqlExpressionResolver sqlExpressionResolver,
-			SqlAstCreationContext creationContext) {
-		final CompositeTableGroup compositeTableGroup = new CompositeTableGroup(
-				navigablePath,
-				this,
-				lhs
-		);
-
-		final TableGroupJoin join = new TableGroupJoin( navigablePath, SqlAstJoinType.LEFT, compositeTableGroup, null );
-		lhs.addTableGroupJoin( join );
-
-		return join;
-	}
-
 	@Override
 	public String getSqlAliasStem() {
 		return "id";
 	}
 
-	@Override
-	public ModelPart findSubPart(String name, EntityMappingType treatTargetType) {
-		return getMappedTypeDescriptor().findSubPart( name, treatTargetType );
-	}
-
-	@Override
-	public void visitSubParts(Consumer<ModelPart> consumer, EntityMappingType treatTargetType) {
-		getMappedTypeDescriptor().visitSubParts( consumer, treatTargetType );
-	}
-
 	@Override
 	public String getFetchableName() {
 		return "id";
 	}
 
-	@Override
-	public FetchOptions getMappedFetchOptions() {
-		return this;
-	}
-
-	@Override
-	public Fetch generateFetch(
-			FetchParent fetchParent,
-			NavigablePath fetchablePath,
-			FetchTiming fetchTiming,
-			boolean selected,
-			LockMode lockMode,
-			String resultVariable,
-			DomainResultCreationState creationState) {
-		return new EmbeddableFetchImpl(
-				fetchablePath,
-				this,
-				fetchParent,
-				fetchTiming,
-				selected,
-				attributeMetadataAccess.resolveAttributeMetadata( null ).isNullable(),
-				creationState
-		);
-	}
-
 	@Override
 	public int getNumberOfFetchables() {
 		return idAttributeMappings.size();
 	}
 
-	@Override
-	public FetchStyle getStyle() {
-		return FetchStyle.JOIN;
-	}
-
-	@Override
-	public FetchTiming getTiming() {
-		return FetchTiming.IMMEDIATE;
-	}
 }

hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/ToOneAttributeMapping.java

@@ -25,6 +25,7 @@ import org.hibernate.metamodel.mapping.StateArrayContributorMetadataAccess;
 import org.hibernate.metamodel.model.domain.NavigableRole;
 import org.hibernate.persister.entity.EntityPersister;
 import org.hibernate.property.access.spi.PropertyAccess;
+import org.hibernate.query.EntityIdentifierNavigablePath;
 import org.hibernate.query.NavigablePath;
 import org.hibernate.sql.ast.SqlAstJoinType;
 import org.hibernate.sql.ast.spi.FromClauseAccess;
@@ -50,8 +51,8 @@ import org.hibernate.sql.results.graph.entity.internal.EntityDelayedFetchImpl;
 import org.hibernate.sql.results.graph.entity.internal.EntityFetchJoinedImpl;
 import org.hibernate.sql.results.graph.entity.internal.EntityFetchSelectImpl;
 import org.hibernate.sql.results.graph.entity.internal.EntityResultJoinedSubclassImpl;
-import org.hibernate.sql.results.internal.domain.CircularFetchImpl;
 import org.hibernate.sql.results.internal.domain.CircularBiDirectionalFetchImpl;
+import org.hibernate.sql.results.internal.domain.CircularFetchImpl;
 import org.hibernate.type.ForeignKeyDirection;
 
 /**
@@ -227,7 +228,7 @@ public class ToOneAttributeMapping extends AbstractSingularAttributeMapping
 			NavigablePath parentNavigablePath = fetchablePath.getParent();
 			ModelPart modelPart = creationState.resolveModelPart( parentNavigablePath );
 			if ( modelPart instanceof EmbeddedIdentifierMappingImpl ) {
-				while ( parentNavigablePath.getFullPath().endsWith( EntityIdentifierMapping.ROLE_LOCAL_NAME ) ) {
+				while ( parentNavigablePath instanceof EntityIdentifierNavigablePath ) {
 					parentNavigablePath = parentNavigablePath.getParent();
 				}
 			}
@@ -340,7 +341,7 @@ public class ToOneAttributeMapping extends AbstractSingularAttributeMapping
 		}
 
 		if ( modelPart instanceof EntityCollectionPart ) {
-			if ( parentOfParent.getFullPath().endsWith( EntityIdentifierMapping.ROLE_LOCAL_NAME ) ) {
+			if ( parentOfParent instanceof EntityIdentifierNavigablePath ) {
 				parentOfParent = parentOfParent.getParent();
 			}
 			return ( (PluralAttributeMapping) creationState.resolveModelPart( parentOfParent ) ).isBidirectionalAttributeName(

hibernate-core/src/main/java/org/hibernate/query/EntityIdentifierNavigablePath.java

@@ -0,0 +1,24 @@
+/*
+ * 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.query;
+
+import org.hibernate.metamodel.mapping.EntityIdentifierMapping;
+
+/**
+ * @author Andrea Boriero
+ */
+public class EntityIdentifierNavigablePath extends NavigablePath {
+
+	public EntityIdentifierNavigablePath(NavigablePath parent) {
+		super( parent, EntityIdentifierMapping.ROLE_LOCAL_NAME );
+	}
+
+	@Override
+	public String getLocalName() {
+		return EntityIdentifierMapping.ROLE_LOCAL_NAME;
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/sqm/sql/internal/StandardSqmSelectTranslator.java

@@ -18,6 +18,7 @@ import org.hibernate.HibernateException;
 import org.hibernate.LockMode;
 import org.hibernate.LockOptions;
 import org.hibernate.NotYetImplementedFor6Exception;
+import org.hibernate.collection.spi.BagSemantics;
 import org.hibernate.engine.FetchTiming;
 import org.hibernate.engine.profile.FetchProfile;
 import org.hibernate.engine.spi.LoadQueryInfluencers;
@@ -26,6 +27,7 @@ import org.hibernate.internal.FilterHelper;
 import org.hibernate.internal.util.collections.CollectionHelper;
 import org.hibernate.internal.util.collections.Stack;
 import org.hibernate.internal.util.collections.StandardStack;
+import org.hibernate.loader.MultipleBagFetchException;
 import org.hibernate.metamodel.mapping.CollectionPart;
 import org.hibernate.metamodel.mapping.EntityMappingType;
 import org.hibernate.metamodel.mapping.ModelPart;
@@ -271,6 +273,7 @@ public class StandardSqmSelectTranslator
 	@Override
 	public List<Fetch> visitFetches(FetchParent fetchParent) {
 		final List<Fetch> fetches = CollectionHelper.arrayList( fetchParent.getReferencedMappingType().getNumberOfFetchables() );
+		final List<String> bagRoles = new ArrayList<>();
 
 		final BiConsumer<Fetchable, Boolean> fetchableBiConsumer = (fetchable, isKeyFetchable) -> {
 				final NavigablePath fetchablePath = fetchParent.getNavigablePath().append( fetchable.getFetchableName() );
@@ -291,6 +294,12 @@ public class StandardSqmSelectTranslator
 					final Fetch fetch = buildFetch( fetchablePath, fetchParent, fetchable, isKeyFetchable );
 
 					if ( fetch != null ) {
+						if ( fetch.getTiming() == FetchTiming.IMMEDIATE &&
+								fetchable instanceof PluralAttributeMapping &&
+								( (PluralAttributeMapping) fetchable ).getMappedTypeDescriptor()
+										.getCollectionSemantics() instanceof BagSemantics ) {
+							bagRoles.add( fetchable.getNavigableRole().getNavigableName() );
+						}
 						fetches.add( fetch );
 					}
 				}
@@ -304,7 +313,9 @@ public class StandardSqmSelectTranslator
 //		fetchParent.getReferencedMappingContainer().visitFetchables( fetchableBiConsumer, treatTargetType );
 		fetchParent.getReferencedMappingContainer().visitKeyFetchables( fetchable -> fetchableBiConsumer.accept( fetchable, true ), null );
 		fetchParent.getReferencedMappingContainer().visitFetchables( fetchable -> fetchableBiConsumer.accept( fetchable, false ), null );
-
+		if ( bagRoles.size() > 1 ) {
+			throw new MultipleBagFetchException( bagRoles );
+		}
 		return fetches;
 	}
 

hibernate-core/src/main/java/org/hibernate/sql/results/graph/entity/AbstractEntityResultGraphNode.java

@@ -19,6 +19,7 @@ import org.hibernate.metamodel.mapping.ManagedMappingType;
 import org.hibernate.metamodel.mapping.internal.SingleAttributeIdentifierMapping;
 import org.hibernate.metamodel.mapping.internal.ToOneAttributeMapping;
 import org.hibernate.persister.entity.AbstractEntityPersister;
+import org.hibernate.query.EntityIdentifierNavigablePath;
 import org.hibernate.query.NavigablePath;
 import org.hibernate.sql.ast.tree.from.TableGroup;
 import org.hibernate.sql.results.graph.AbstractFetchParent;
@@ -71,7 +72,7 @@ public abstract class AbstractEntityResultGraphNode extends AbstractFetchParent
 			identifierResult = null;
 			if ( identifierMapping instanceof SingleAttributeIdentifierMapping ) {
 				identifierMapping.createDomainResult(
-						navigablePath.append( EntityIdentifierMapping.ROLE_LOCAL_NAME ),
+						new EntityIdentifierNavigablePath( navigablePath ),
 						entityTableGroup,
 						null,
 						creationState
@@ -83,7 +84,7 @@ public abstract class AbstractEntityResultGraphNode extends AbstractFetchParent
 		}
 		else {
 			identifierResult = identifierMapping.createDomainResult(
-					navigablePath.append( EntityIdentifierMapping.ROLE_LOCAL_NAME ),
+					new EntityIdentifierNavigablePath( navigablePath ),
 					entityTableGroup,
 					null,
 					creationState
@@ -141,7 +142,7 @@ public abstract class AbstractEntityResultGraphNode extends AbstractFetchParent
 				attributeMapping -> {
 					if ( attributeMapping instanceof ToOneAttributeMapping ) {
 						( (ToOneAttributeMapping) attributeMapping ).getForeignKeyDescriptor().createDomainResult(
-								navigablePath.append( EntityIdentifierMapping.ROLE_LOCAL_NAME ),
+								new EntityIdentifierNavigablePath( navigablePath ),
 								entityTableGroup,
 								null,
 								creationState
@@ -149,7 +150,7 @@ public abstract class AbstractEntityResultGraphNode extends AbstractFetchParent
 					}
 					else {
 						attributeMapping.createDomainResult(
-								navigablePath.append( EntityIdentifierMapping.ROLE_LOCAL_NAME ),
+								new EntityIdentifierNavigablePath( navigablePath ),
 								entityTableGroup,
 								null,
 								creationState

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

@@ -0,0 +1,217 @@
+/*
+ * 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.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.loader.MultipleBagFetchException;
+
+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.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
+
+@DomainModel(
+		annotatedClasses = {
+				MultipleBagFetchHqlTest.Post.class,
+				MultipleBagFetchHqlTest.PostComment.class,
+				MultipleBagFetchHqlTest.Tag.class
+		}
+)
+@SessionFactory
+public class MultipleBagFetchHqlTest {
+
+	@BeforeEach
+	public void setUp(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					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 );
+				}
+		);
+	}
+
+	@AfterEach
+	public void tearDown(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					session.createQuery( "delete from Post" ).executeUpdate();
+					session.createQuery( "delete from Tag" ).executeUpdate();
+					session.createQuery( "delete from PostComment" ).executeUpdate();
+				}
+		);
+	}
+
+	@Test
+	public void testMultipleBagFetchHql(SessionFactoryScope scope) {
+		scope.inSession(
+				session -> {
+					try {
+						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() ) );
+					}
+				}
+		);
+	}
+
+	@Test
+	public void testSingleBagFetchHql(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					session.createQuery(
+							"select p " +
+									"from Post p " +
+									"join fetch p.tags " +
+									"join p.comments " +
+									"where p.id = :id"
+					).setParameter( "id", 1L ).uniqueResult();
+				}
+		);
+	}
+
+	@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<>();
+
+		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/orm/test/collection/bag/MultipleBagFetchTest.java

@@ -4,7 +4,7 @@
  * 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;
+package org.hibernate.orm.test.collection.bag;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -21,12 +21,11 @@ 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 org.junit.jupiter.api.Test;
 
-import static org.junit.Assert.fail;
+import static org.junit.jupiter.api.Assertions.fail;
 
 public class MultipleBagFetchTest {
 

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

@@ -1,195 +0,0 @@
-/*
- * 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;
-		}
-	}
-}