preliminary support for collections - lists and sets tested (excluding entity-valued elements and map-key)

hibernate-core/src/main/java/org/hibernate/boot/model/process/internal/EnumeratedValueResolution.java

@@ -36,7 +36,8 @@ public class EnumeratedValueResolution<E extends Enum<E>> implements BasicValue.
 		this.domainJtd = domainJtd;
 		this.jdbcJtd = jdbcJtd;
 		this.std = std;
-		this.valueConverter = valueConverter;
+//		this.valueConverter = valueConverter;
+		this.valueConverter = null;
 	}
 
 	@Override

hibernate-core/src/main/java/org/hibernate/boot/spi/MetadataBuildingOptions.java

@@ -25,6 +25,7 @@ import org.hibernate.boot.model.relational.AuxiliaryDatabaseObject;
 import org.hibernate.boot.registry.StandardServiceRegistry;
 import org.hibernate.cache.spi.access.AccessType;
 import org.hibernate.cfg.MetadataSourceType;
+import org.hibernate.collection.internal.StandardCollectionSemanticsResolver;
 import org.hibernate.collection.spi.CollectionSemanticsResolver;
 import org.hibernate.dialect.function.SQLFunction;
 import org.hibernate.metamodel.internal.StandardManagedTypeRepresentationResolver;
@@ -61,7 +62,8 @@ public interface MetadataBuildingOptions {
 	}
 
 	default CollectionSemanticsResolver getPersistentCollectionRepresentationResolver() {
-		throw new NotYetImplementedFor6Exception( getClass() );
+		// for now always return the standard one
+		return StandardCollectionSemanticsResolver.INSTANCE;
 	}
 
 	/**

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

@@ -21,6 +21,8 @@ import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.internal.CoreMessageLogger;
 import org.hibernate.loader.CollectionAliases;
 import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.RowProcessingState;
 import org.hibernate.type.Type;
 
 import org.jboss.logging.Logger;
@@ -190,6 +192,31 @@ public class PersistentArrayHolder extends AbstractPersistentCollection {
 		return element;
 	}
 
+	@Override
+	public Object readFrom(
+			RowProcessingState rowProcessingState,
+			DomainResultAssembler elementAssembler,
+			DomainResultAssembler indexAssembler,
+			DomainResultAssembler identifierAssembler,
+			Object owner) throws HibernateException {
+		assert elementAssembler != null;
+		assert indexAssembler != null;
+		assert identifierAssembler == null;
+
+		final Object element = elementAssembler.assemble( rowProcessingState );
+		final int index = (int) indexAssembler.assemble( rowProcessingState );
+
+		for ( int i = tempList.size(); i<=index; i++) {
+			//noinspection unchecked
+			tempList.add( i, null );
+		}
+
+		//noinspection unchecked
+		tempList.set( index, element );
+
+		return element;
+	}
+
 	@Override
 	@SuppressWarnings("unchecked")
 	public Iterator entries(CollectionPersister persister) {

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

@@ -22,6 +22,8 @@ import org.hibernate.engine.spi.SessionImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.loader.CollectionAliases;
 import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.RowProcessingState;
 import org.hibernate.type.Type;
 
 /**
@@ -133,6 +135,24 @@ public class PersistentBag extends AbstractPersistentCollection implements List
 		return element;
 	}
 
+	@Override
+	public Object readFrom(
+			RowProcessingState rowProcessingState,
+			DomainResultAssembler elementAssembler,
+			DomainResultAssembler indexAssembler,
+			DomainResultAssembler identifierAssembler,
+			Object owner) throws HibernateException {
+		assert indexAssembler == null;
+		assert identifierAssembler == null;
+
+		final Object element = elementAssembler.assemble( rowProcessingState );
+		if ( element != null ) {
+			//noinspection unchecked
+			bag.add( element );
+		}
+		return element;
+	}
+
 	@Override
 	public void beforeInitialize(CollectionPersister persister, int anticipatedSize) {
 		this.bag = (List) persister.getCollectionType().instantiate( anticipatedSize );

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

@@ -22,6 +22,8 @@ import org.hibernate.engine.spi.SessionImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.loader.CollectionAliases;
 import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.RowProcessingState;
 import org.hibernate.type.Type;
 
 /**
@@ -372,6 +374,30 @@ public class PersistentIdentifierBag extends AbstractPersistentCollection implem
 		return element;
 	}
 
+	@Override
+	public Object readFrom(
+			RowProcessingState rowProcessingState,
+			DomainResultAssembler elementAssembler,
+			DomainResultAssembler indexAssembler,
+			DomainResultAssembler identifierAssembler,
+			Object owner) throws HibernateException {
+		assert indexAssembler == null;
+		final Object element = elementAssembler.assemble( rowProcessingState );
+		final Object identifier = identifierAssembler.assemble( rowProcessingState );
+
+		final Object old = identifiers.put(
+				values.size(),
+				identifier
+		);
+
+		if ( old == null ) {
+			//maintain correct duplication if loaded in a cartesian product
+			values.add( element );
+		}
+
+		return element;
+	}
+
 	@Override
 	@SuppressWarnings("unchecked")
 	public Serializable getSnapshot(CollectionPersister persister) throws HibernateException {

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

@@ -20,6 +20,8 @@ import org.hibernate.engine.spi.SessionImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.loader.CollectionAliases;
 import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.RowProcessingState;
 import org.hibernate.type.Type;
 
 /**
@@ -206,9 +208,9 @@ public class PersistentList extends AbstractPersistentCollection implements List
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public boolean containsAll(Collection coll) {
 		read();
+		//noinspection unchecked
 		return list.containsAll( coll );
 	}
 
@@ -262,9 +264,9 @@ public class PersistentList extends AbstractPersistentCollection implements List
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public boolean retainAll(Collection coll) {
 		initialize( true );
+		//noinspection unchecked
 		if ( list.retainAll( coll ) ) {
 			dirty();
 			return true;
@@ -275,7 +277,6 @@ public class PersistentList extends AbstractPersistentCollection implements List
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public void clear() {
 		if ( isClearQueueEnabled() ) {
 			queueOperation( new Clear() );
@@ -290,7 +291,6 @@ public class PersistentList extends AbstractPersistentCollection implements List
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public Object get(int index) {
 		if ( index < 0 ) {
 			throw new ArrayIndexOutOfBoundsException( "negative index" );
@@ -300,7 +300,6 @@ public class PersistentList extends AbstractPersistentCollection implements List
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public Object set(int index, Object value) {
 		if (index<0) {
 			throw new ArrayIndexOutOfBoundsException("negative index");
@@ -310,6 +309,7 @@ public class PersistentList extends AbstractPersistentCollection implements List
 
 		if ( old==UNKNOWN ) {
 			write();
+			//noinspection unchecked
 			return list.set( index, value );
 		}
 		else {
@@ -319,7 +319,6 @@ public class PersistentList extends AbstractPersistentCollection implements List
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public Object remove(int index) {
 		if ( index < 0 ) {
 			throw new ArrayIndexOutOfBoundsException( "negative index" );
@@ -338,45 +337,40 @@ public class PersistentList extends AbstractPersistentCollection implements List
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public void add(int index, Object value) {
 		if ( index < 0 ) {
 			throw new ArrayIndexOutOfBoundsException( "negative index" );
 		}
 		write();
+		//noinspection unchecked
 		list.add( index, value );
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public int indexOf(Object value) {
 		read();
 		return list.indexOf( value );
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public int lastIndexOf(Object value) {
 		read();
 		return list.lastIndexOf( value );
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public ListIterator listIterator() {
 		read();
 		return new ListIteratorProxy( list.listIterator() );
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public ListIterator listIterator(int index) {
 		read();
 		return new ListIteratorProxy( list.listIterator( index ) );
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public java.util.List subList(int from, int to) {
 		read();
 		return new ListProxy( list.subList( from, to ) );
@@ -409,6 +403,32 @@ public class PersistentList extends AbstractPersistentCollection implements List
 		return element;
 	}
 
+	@Override
+	public Object readFrom(
+			RowProcessingState rowProcessingState,
+			DomainResultAssembler elementAssembler,
+			DomainResultAssembler indexAssembler,
+			DomainResultAssembler identifierAssembler,
+			Object owner) throws HibernateException {
+		assert elementAssembler != null;
+		assert indexAssembler != null;
+		assert identifierAssembler == null;
+
+		final Object element = elementAssembler.assemble( rowProcessingState );
+		final int index = (int) indexAssembler.assemble( rowProcessingState );
+
+		//pad with nulls from the current last element up to the new index
+		for ( int i = list.size(); i<=index; i++) {
+			//noinspection unchecked
+			list.add( i, null );
+		}
+
+		//noinspection unchecked
+		list.set( index, element );
+
+		return element;
+	}
+
 	@Override
 	@SuppressWarnings("unchecked")
 	public Iterator entries(CollectionPersister persister) {

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

@@ -22,6 +22,8 @@ import org.hibernate.engine.spi.SessionImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.loader.CollectionAliases;
 import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.RowProcessingState;
 import org.hibernate.type.Type;
 
 
@@ -176,7 +178,6 @@ public class PersistentMap extends AbstractPersistentCollection implements Map {
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public Object put(Object key, Object value) {
 		if ( isPutQueueEnabled() ) {
 			final Object old = readElementByIndex( key );
@@ -186,6 +187,7 @@ public class PersistentMap extends AbstractPersistentCollection implements Map {
 			}
 		}
 		initialize( true );
+		//noinspection unchecked
 		final Object old = map.put( key, value );
 		// would be better to use the element-type to determine
 		// whether the old and the new are equal here; the problem being
@@ -198,7 +200,6 @@ public class PersistentMap extends AbstractPersistentCollection implements Map {
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public Object remove(Object key) {
 		if ( isPutQueueEnabled() ) {
 			final Object old = readElementByIndex( key );
@@ -218,7 +219,6 @@ public class PersistentMap extends AbstractPersistentCollection implements Map {
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public void putAll(Map puts) {
 		if ( puts.size() > 0 ) {
 			initialize( true );
@@ -230,7 +230,6 @@ public class PersistentMap extends AbstractPersistentCollection implements Map {
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public void clear() {
 		if ( isClearQueueEnabled() ) {
 			queueOperation( new Clear() );
@@ -245,34 +244,29 @@ public class PersistentMap extends AbstractPersistentCollection implements Map {
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public Set keySet() {
 		read();
 		return new SetProxy( map.keySet() );
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public Collection values() {
 		read();
 		return new SetProxy( map.values() );
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public Set entrySet() {
 		read();
 		return new EntrySetProxy( map.entrySet() );
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public boolean empty() {
 		return map.isEmpty();
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public String toString() {
 		read();
 		return map.toString();
@@ -281,7 +275,6 @@ public class PersistentMap extends AbstractPersistentCollection implements Map {
 	private transient List<Object[]> loadingEntries;
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public Object readFrom(
 			ResultSet rs,
 			CollectionPersister persister,
@@ -298,6 +291,30 @@ public class PersistentMap extends AbstractPersistentCollection implements Map {
 		return element;
 	}
 
+	@Override
+	public Object readFrom(
+			RowProcessingState rowProcessingState,
+			DomainResultAssembler elementAssembler,
+			DomainResultAssembler indexAssembler,
+			DomainResultAssembler identifierAssembler,
+			Object owner) throws HibernateException {
+		assert elementAssembler != null;
+		assert indexAssembler != null;
+		assert identifierAssembler == null;
+
+		final Object element = elementAssembler.assemble( rowProcessingState );
+
+		if ( element != null ) {
+			final Object index = indexAssembler.assemble( rowProcessingState );
+			if ( loadingEntries == null ) {
+				loadingEntries = new ArrayList<>();
+			}
+			loadingEntries.add( new Object[] { index, element } );
+		}
+
+		return element;
+	}
+
 	@Override
 	@SuppressWarnings("unchecked")
 	public boolean endRead() {

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

@@ -21,6 +21,8 @@ import org.hibernate.engine.spi.SessionImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.loader.CollectionAliases;
 import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.RowProcessingState;
 import org.hibernate.type.Type;
 
 
@@ -342,6 +344,27 @@ public class PersistentSet extends AbstractPersistentCollection implements java.
 		return element;
 	}
 
+	@Override
+	public Object readFrom(
+			RowProcessingState rowProcessingState,
+			DomainResultAssembler elementAssembler,
+			DomainResultAssembler indexAssembler,
+			DomainResultAssembler identifierAssembler,
+			Object owner) throws HibernateException {
+		assert elementAssembler != null;
+		assert indexAssembler == null;
+		assert identifierAssembler == null;
+
+		final Object element = elementAssembler.assemble( rowProcessingState );
+
+		if ( element != null ) {
+			//noinspection unchecked
+			tempList.add( element );
+		}
+
+		return element;
+	}
+
 	@Override
 	@SuppressWarnings("unchecked")
 	public void beginRead() {

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

@@ -0,0 +1,84 @@
+/*
+ * 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.internal;
+
+import org.hibernate.MappingException;
+import org.hibernate.NotYetImplementedFor6Exception;
+import org.hibernate.collection.spi.CollectionSemantics;
+import org.hibernate.collection.spi.CollectionSemanticsResolver;
+import org.hibernate.mapping.Array;
+import org.hibernate.mapping.Bag;
+import org.hibernate.mapping.Collection;
+import org.hibernate.mapping.IdentifierBag;
+import org.hibernate.mapping.List;
+import org.hibernate.mapping.Map;
+import org.hibernate.mapping.PrimitiveArray;
+import org.hibernate.mapping.Set;
+
+/**
+ * Standard implementation of CollectionSemanticsResolver
+ *
+ * @author Steve Ebersole
+ */
+public class StandardCollectionSemanticsResolver implements CollectionSemanticsResolver {
+	/**
+	 * Singleton access
+	 */
+	public static final StandardCollectionSemanticsResolver INSTANCE = new StandardCollectionSemanticsResolver();
+
+	@Override
+	public CollectionSemantics resolveRepresentation(Collection bootDescriptor) {
+		if ( bootDescriptor instanceof PrimitiveArray ) {
+			throw new NotYetImplementedFor6Exception();
+		}
+
+		if ( bootDescriptor instanceof Array ) {
+			return StandardArraySemantics.INSTANCE;
+		}
+
+		if ( bootDescriptor instanceof Bag ) {
+			return StandardBagSemantics.INSTANCE;
+		}
+
+		if ( bootDescriptor instanceof IdentifierBag ) {
+			return StandardIdentifierBagSemantics.INSTANCE;
+		}
+		
+		if ( bootDescriptor instanceof List ) {
+			return StandardListSemantics.INSTANCE;
+		}
+
+		if ( bootDescriptor instanceof Map ) {
+			if ( bootDescriptor.isSorted() ) {
+				return StandardSortedMapSemantics.INSTANCE;
+			}
+
+			if ( bootDescriptor.hasOrder() ) {
+				return StandardOrderedMapSemantics.INSTANCE;
+			}
+
+			return StandardMapSemantics.INSTANCE;
+		}
+
+		if ( bootDescriptor instanceof Set ) {
+			if ( bootDescriptor.isSorted() ) {
+				return StandardSortedSetSemantics.INSTANCE;
+			}
+
+			if ( bootDescriptor.hasOrder() ) {
+				return StandardOrderedSetSemantics.INSTANCE;
+			}
+
+			return StandardSetSemantics.INSTANCE;
+		}
+
+		throw new MappingException(
+				"Unexpected org.hibernate.mapping.Collection impl ["
+						+  bootDescriptor + "]; unknown CollectionSemantics"
+		);
+	}
+}

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

@@ -9,6 +9,7 @@ package org.hibernate.collection.spi;
 import java.util.Iterator;
 import java.util.function.Consumer;
 
+import org.hibernate.Incubating;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.persister.collection.CollectionPersister;
@@ -22,6 +23,7 @@ import org.hibernate.persister.collection.CollectionPersister;
  * @author Steve Ebersole
  * @author Gavin King
  */
+@Incubating
 public interface CollectionSemantics<C> {
 	/**
 	 * Get the classification of collections described by this semantic

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

@@ -6,9 +6,12 @@
  */
 package org.hibernate.collection.spi;
 
+import org.hibernate.Incubating;
 import org.hibernate.mapping.Collection;
 
 /**
+ * Resolve the collection semantics for the given mapped collection
+ *
  * todo (6.0) ...
  *
  * Ideally would act as the contract that allows pluggable resolution of
@@ -17,6 +20,7 @@ import org.hibernate.mapping.Collection;
  *
  * @author Steve Ebersole
  */
+@Incubating
 public interface CollectionSemanticsResolver {
 	// really need some form of access to the attribute site
 	CollectionSemantics resolveRepresentation(Collection bootDescriptor);

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

@@ -16,6 +16,8 @@ import org.hibernate.HibernateException;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.loader.CollectionAliases;
 import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.RowProcessingState;
 import org.hibernate.type.Type;
 
 /**
@@ -173,6 +175,13 @@ public interface PersistentCollection {
 	Object readFrom(ResultSet rs, CollectionPersister role, CollectionAliases descriptor, Object owner)
 			throws HibernateException, SQLException;
 
+	Object readFrom(
+			RowProcessingState rowProcessingState,
+			DomainResultAssembler elementAssembler,
+			DomainResultAssembler indexAssembler,
+			DomainResultAssembler identifierAssembler,
+			Object owner) throws HibernateException;
+
 	/**
 	 * Get the identifier of the given collection entry.  This refers to the collection identifier, not the
 	 * identifier of the (possibly) entity elements.  This is only valid for invocation on the

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

@@ -0,0 +1,25 @@
+/*
+ * 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.mapping;
+
+import org.hibernate.metamodel.CollectionClassification;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.results.spi.DomainResult;
+import org.hibernate.sql.results.spi.DomainResultCreationState;
+
+/**
+ * Descriptor for the collection identifier.  Only used with {@link CollectionClassification#IDBAG} collections
+ *
+ * @author Steve Ebersole
+ */
+public interface CollectionIdentifierDescriptor {
+	DomainResult createDomainResult(
+			NavigablePath collectionPath,
+			TableGroup tableGroup,
+			DomainResultCreationState creationState);
+}

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

@@ -15,5 +15,5 @@ import org.hibernate.collection.spi.CollectionSemantics;
  * @author Steve Ebersole
  */
 public interface CollectionMappingType<C> extends MappingType {
-	CollectionSemantics<C> getCCollectionSemantics();
+	CollectionSemantics<C> getCollectionSemantics();
 }

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

@@ -0,0 +1,48 @@
+/*
+ * 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.mapping;
+
+import org.hibernate.sql.results.spi.Fetchable;
+
+/**
+ * @author Steve Ebersole
+ */
+public interface CollectionPart extends ModelPart, Fetchable {
+	enum Nature {
+		ELEMENT( "{element}" ),
+		INDEX( "{index}" );
+
+		private final String name;
+
+		Nature(String name) {
+			this.name = name;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public static Nature fromName(String name) {
+			if ( ELEMENT.name.equals( name ) ) {
+				return ELEMENT;
+			}
+			else if ( INDEX.name.equals( name ) ) {
+				return INDEX;
+			}
+
+			throw new IllegalArgumentException(
+					"Unrecognized CollectionPart Nature name [" + name
+							+ "]; expecting `" + ELEMENT.name + "` or `"
+							+ INDEX.name + "`"
+			);
+		}
+	}
+
+	Nature getNature();
+
+	ModelPart getPartTypeDescriptor();
+}

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

@@ -102,6 +102,7 @@ public class EmbeddableMappingType implements ManagedMappingType {
 			CompositeType compositeType,
 			MappingModelCreationProcess creationProcess) {
 		final String containingTableExpression = valueMapping.getContainingTableExpression();
+
 		final List<String> mappedColumnExpressions = valueMapping.getMappedColumnExpressions();
 
 		final Type[] subtypes = compositeType.getSubtypes();
@@ -196,6 +197,11 @@ public class EmbeddableMappingType implements ManagedMappingType {
 		throw new NotYetImplementedFor6Exception( getClass() );
 	}
 
+	@Override
+	public int getNumberOfFetchables() {
+		return attributeMappings.size();
+	}
+
 	@Override
 	public void visitFetchables(
 			Consumer<Fetchable> fetchableConsumer,

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

@@ -14,12 +14,13 @@ import org.hibernate.sql.ast.Clause;
 import org.hibernate.sql.ast.tree.expression.Expression;
 import org.hibernate.sql.ast.tree.from.TableGroup;
 import org.hibernate.sql.ast.tree.from.TableGroupJoinProducer;
+import org.hibernate.sql.results.spi.Fetchable;
 import org.hibernate.sql.results.spi.FetchableContainer;
 
 /**
  * @author Steve Ebersole
  */
-public interface EmbeddableValuedModelPart extends ModelPart, FetchableContainer, TableGroupJoinProducer {
+public interface EmbeddableValuedModelPart extends ModelPart, Fetchable, FetchableContainer, TableGroupJoinProducer {
 	EmbeddableMappingType getEmbeddableTypeDescriptor();
 
 	/**

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

@@ -0,0 +1,19 @@
+/*
+ * 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.mapping;
+
+import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.results.spi.DomainResult;
+import org.hibernate.sql.results.spi.DomainResultCreationState;
+
+/**
+ * @author Steve Ebersole
+ */
+public interface ForeignKeyDescriptor {
+	DomainResult createDomainResult(NavigablePath collectionPath, TableGroup tableGroup, DomainResultCreationState creationState);
+}

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

@@ -6,15 +6,39 @@
  */
 package org.hibernate.metamodel.mapping;
 
+import java.util.function.Consumer;
+
 import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.sql.ast.tree.from.TableGroupJoinProducer;
+import org.hibernate.sql.results.spi.Fetchable;
+import org.hibernate.sql.results.spi.FetchableContainer;
 
 /**
  * @author Steve Ebersole
  */
-public interface PluralAttributeMapping extends AttributeMapping, StateArrayContributorMapping {
+public interface PluralAttributeMapping
+		extends AttributeMapping, StateArrayContributorMapping, TableGroupJoinProducer, FetchableContainer {
+
 	CollectionPersister getCollectionDescriptor();
 
-	ModelPart getValueDescriptor();
+	ForeignKeyDescriptor getKeyDescriptor();
 
-	ModelPart getIndexDescriptor();
+	CollectionPart getIndexDescriptor();
+
+	CollectionPart getElementDescriptor();
+
+	CollectionIdentifierDescriptor getIdentifierDescriptor();
+
+	@Override
+	default void visitKeyFetchables(Consumer<Fetchable> fetchableConsumer, EntityMappingType treatTargetType) {
+		final CollectionPart indexDescriptor = getIndexDescriptor();
+		if ( indexDescriptor != null ) {
+			fetchableConsumer.accept( indexDescriptor );
+		}
+	}
+
+	@Override
+	default void visitFetchables(Consumer<Fetchable> fetchableConsumer, EntityMappingType treatTargetType) {
+		fetchableConsumer.accept( getElementDescriptor() );
+	}
 }

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

@@ -13,14 +13,17 @@ import org.hibernate.LockMode;
 import org.hibernate.engine.FetchStrategy;
 import org.hibernate.engine.FetchTiming;
 import org.hibernate.metamodel.mapping.BasicValuedModelPart;
+import org.hibernate.metamodel.mapping.CollectionPart;
 import org.hibernate.metamodel.mapping.JdbcMapping;
 import org.hibernate.metamodel.mapping.MappingType;
 import org.hibernate.metamodel.model.convert.spi.BasicValueConverter;
+import org.hibernate.persister.collection.CollectionPersister;
 import org.hibernate.query.NavigablePath;
 import org.hibernate.query.sqm.sql.SqlExpressionResolver;
 import org.hibernate.sql.ast.spi.SqlSelection;
 import org.hibernate.sql.ast.tree.expression.ColumnReference;
 import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.results.SqlResultsLogger;
 import org.hibernate.sql.results.internal.domain.basic.BasicFetch;
 import org.hibernate.sql.results.internal.domain.basic.BasicResult;
 import org.hibernate.sql.results.spi.DomainResult;
@@ -36,13 +39,24 @@ import org.hibernate.type.spi.TypeConfiguration;
  *
  * @author Steve Ebersole
  */
-public class BasicValuedCollectionPart implements BasicValuedModelPart {
+public class BasicValuedCollectionPart implements CollectionPart, BasicValuedModelPart {
+
+	private final CollectionPersister collectionDescriptor;
+	private final Nature nature;
+	private final BasicType mapper;
+	private final BasicValueConverter valueConverter;
+
+	private final String tableExpression;
+	private final String columnExpression;
+
 	public BasicValuedCollectionPart(
+			CollectionPersister collectionDescriptor,
 			Nature nature,
 			BasicType mapper,
 			BasicValueConverter valueConverter,
 			String tableExpression,
 			String columnExpression) {
+		this.collectionDescriptor = collectionDescriptor;
 		this.nature = nature;
 		this.mapper = mapper;
 		this.valueConverter = valueConverter;
@@ -50,14 +64,15 @@ public class BasicValuedCollectionPart implements BasicValuedModelPart {
 		this.columnExpression = columnExpression;
 	}
 
-	enum Nature { ELEMENT, INDEX }
+	@Override
+	public Nature getNature() {
+		return nature;
+	}
 
-	private final Nature nature;
-	private final BasicType mapper;
-	private final BasicValueConverter valueConverter;
-
-	private final String tableExpression;
-	private final String columnExpression;
+	@Override
+	public BasicType getPartTypeDescriptor() {
+		return mapper;
+	}
 
 	@Override
 	public String getContainingTableExpression() {
@@ -91,7 +106,9 @@ public class BasicValuedCollectionPart implements BasicValuedModelPart {
 		return new BasicResult(
 				sqlSelection.getValuesArrayPosition(),
 				resultVariable,
-				getJavaTypeDescriptor()
+				getJavaTypeDescriptor(),
+				valueConverter,
+				navigablePath
 		);
 	}
 
@@ -100,9 +117,9 @@ public class BasicValuedCollectionPart implements BasicValuedModelPart {
 
 		return exprResolver.resolveSqlSelection(
 				exprResolver.resolveSqlExpression(
-						SqlExpressionResolver.createColumnReferenceKey( tableExpression, columnExpression ),
+						SqlExpressionResolver.createColumnReferenceKey( tableGroup.getPrimaryTableReference(), columnExpression ),
 						sqlAstProcessingState -> new ColumnReference(
-								tableGroup.resolveTableReference( tableExpression ).getIdentificationVariable(),
+								tableGroup.getPrimaryTableReference().getIdentificationVariable(),
 								columnExpression,
 								mapper,
 								creationState.getSqlAstCreationState().getCreationContext().getSessionFactory()
@@ -148,6 +165,12 @@ public class BasicValuedCollectionPart implements BasicValuedModelPart {
 			LockMode lockMode,
 			String resultVariable,
 			DomainResultCreationState creationState) {
+		SqlResultsLogger.INSTANCE.debugf(
+				"Generating Fetch for collection-part : `%s` -> `%s`",
+				collectionDescriptor.getRole(),
+				nature.getName()
+		);
+
 		final SqlSelection sqlSelection = resolveSqlSelection(
 				creationState.getSqlAstCreationState().getFromClauseAccess().findTableGroup( fetchablePath.getParent() ),
 				creationState

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

@@ -0,0 +1,83 @@
+/*
+ * 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.mapping.internal;
+
+import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.metamodel.mapping.CollectionIdentifierDescriptor;
+import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.query.sqm.sql.SqlAstCreationState;
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
+import org.hibernate.sql.ast.spi.SqlSelection;
+import org.hibernate.sql.ast.tree.expression.ColumnReference;
+import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.results.internal.domain.basic.BasicResult;
+import org.hibernate.sql.results.spi.DomainResult;
+import org.hibernate.sql.results.spi.DomainResultCreationState;
+import org.hibernate.type.BasicType;
+
+/**
+ * @author Steve Ebersole
+ */
+public class CollectionIdentifierDescriptorImpl implements CollectionIdentifierDescriptor {
+	private final CollectionPersister collectionDescriptor;
+	private final String columnName;
+	private final BasicType type;
+
+	public CollectionIdentifierDescriptorImpl(
+			CollectionPersister collectionDescriptor,
+			String columnName,
+			BasicType type) {
+		this.collectionDescriptor = collectionDescriptor;
+		this.columnName = columnName;
+		this.type = type;
+	}
+
+	@Override
+	public DomainResult createDomainResult(
+			NavigablePath collectionPath,
+			TableGroup tableGroup,
+			DomainResultCreationState creationState) {
+
+
+		final SqlAstCreationState astCreationState = creationState.getSqlAstCreationState();
+		final SqlAstCreationContext astCreationContext = astCreationState.getCreationContext();
+		final SessionFactoryImplementor sessionFactory = astCreationContext.getSessionFactory();
+		final SqlExpressionResolver sqlExpressionResolver = astCreationState.getSqlExpressionResolver();
+
+		final SqlSelection sqlSelection = sqlExpressionResolver.resolveSqlSelection(
+				sqlExpressionResolver.resolveSqlExpression(
+						SqlExpressionResolver.createColumnReferenceKey(
+								tableGroup.getPrimaryTableReference(),
+								columnName
+						),
+						p -> new ColumnReference(
+								tableGroup.getPrimaryTableReference().getIdentificationVariable(),
+								columnName,
+								type,
+								sessionFactory
+						)
+				),
+				type.getJavaTypeDescriptor(),
+				sessionFactory.getTypeConfiguration()
+		);
+
+		//noinspection unchecked
+		return new BasicResult(
+				sqlSelection.getValuesArrayPosition(),
+				null,
+				type.getJavaTypeDescriptor(),
+				collectionPath
+		);
+	}
+
+	@Override
+	public String toString() {
+		return getClass().getSimpleName() + "(" + collectionDescriptor.getRole() + ")";
+	}
+}

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

@@ -31,6 +31,7 @@ import org.hibernate.query.sqm.sql.SqlExpressionResolver;
 import org.hibernate.query.sqm.sql.SqmToSqlAstConverter;
 import org.hibernate.sql.ast.Clause;
 import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBase;
 import org.hibernate.sql.ast.spi.SqlAliasBaseGenerator;
 import org.hibernate.sql.ast.spi.SqlAstCreationContext;
 import org.hibernate.sql.ast.tree.expression.ColumnReference;
@@ -39,7 +40,9 @@ 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.TableGroupProducer;
 import org.hibernate.sql.ast.tree.from.TableReference;
+import org.hibernate.sql.ast.tree.from.TableReferenceCollector;
 import org.hibernate.sql.results.internal.domain.composite.CompositeFetch;
 import org.hibernate.sql.results.internal.domain.composite.CompositeResult;
 import org.hibernate.sql.results.spi.DomainResult;
@@ -162,6 +165,7 @@ public class EmbeddedAttributeMapping
 				this,
 				fetchParent,
 				fetchTiming,
+				getAttributeMetadataAccess().resolveAttributeMetadata( null ).isNullable(),
 				creationState
 		);
 	}
@@ -245,8 +249,44 @@ public class EmbeddedAttributeMapping
 		);
 	}
 
+	@Override
+	public void applyTableReferences(
+			SqlAliasBase sqlAliasBase,
+			JoinType baseJoinType,
+			TableReferenceCollector collector,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext) {
+		getEmbeddableTypeDescriptor().visitAttributeMappings(
+				attrMapping -> {
+					if ( attrMapping instanceof TableGroupProducer ) {
+						( (TableGroupProducer) attrMapping ).applyTableReferences(
+								sqlAliasBase,
+								baseJoinType,
+								collector,
+								sqlExpressionResolver,
+								creationContext
+						);
+					}
+					else if ( attrMapping.getMappedTypeDescriptor() instanceof TableGroupProducer ) {
+						( (TableGroupProducer) attrMapping.getMappedTypeDescriptor() ).applyTableReferences(
+								sqlAliasBase,
+								baseJoinType,
+								collector,
+								sqlExpressionResolver,
+								creationContext
+						);
+					}
+				}
+		);
+	}
+
 	@Override
 	public String getSqlAliasStem() {
 		return getAttributeName();
 	}
+
+	@Override
+	public int getNumberOfFetchables() {
+		return getEmbeddableTypeDescriptor().getNumberOfAttributeMappings();
+	}
 }

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

@@ -0,0 +1,189 @@
+/*
+ * 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.mapping.internal;
+
+import java.util.List;
+import java.util.function.Consumer;
+
+import org.hibernate.LockMode;
+import org.hibernate.NotYetImplementedFor6Exception;
+import org.hibernate.engine.FetchStrategy;
+import org.hibernate.engine.FetchTiming;
+import org.hibernate.metamodel.mapping.CollectionPart;
+import org.hibernate.metamodel.mapping.EmbeddableMappingType;
+import org.hibernate.metamodel.mapping.EmbeddableValuedModelPart;
+import org.hibernate.metamodel.mapping.EntityMappingType;
+import org.hibernate.metamodel.mapping.ModelPart;
+import org.hibernate.metamodel.mapping.SingularAttributeMapping;
+import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.query.sqm.sql.SqlAstCreationState;
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
+import org.hibernate.query.sqm.sql.SqmToSqlAstConverter;
+import org.hibernate.sql.ast.Clause;
+import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBase;
+import org.hibernate.sql.ast.spi.SqlAliasBaseGenerator;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
+import org.hibernate.sql.ast.tree.expression.Expression;
+import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.ast.tree.from.TableGroupJoin;
+import org.hibernate.sql.ast.tree.from.TableReferenceCollector;
+import org.hibernate.sql.results.internal.domain.composite.CompositeFetch;
+import org.hibernate.sql.results.spi.DomainResultCreationState;
+import org.hibernate.sql.results.spi.Fetch;
+import org.hibernate.sql.results.spi.FetchParent;
+import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
+
+/**
+ * @author Steve Ebersole
+ */
+public class EmbeddedCollectionPart implements CollectionPart, EmbeddableValuedModelPart {
+	private final CollectionPersister collectionDescriptor;
+	private final Nature nature;
+	private final EmbeddableMappingType embeddableMappingType;
+
+	private final String containingTableExpression;
+
+	private final SingularAttributeMapping parentInjectionAttribute;
+	private final List<String> columnExpressions;
+	private final String sqlAliasStem;
+
+	@SuppressWarnings("WeakerAccess")
+	public EmbeddedCollectionPart(
+			CollectionPersister collectionDescriptor,
+			Nature nature,
+			EmbeddableMappingType embeddableMappingType,
+			SingularAttributeMapping parentInjectionAttribute,
+			String containingTableExpression,
+			List<String> columnExpressions,
+			String sqlAliasStem) {
+		this.collectionDescriptor = collectionDescriptor;
+		this.nature = nature;
+		this.embeddableMappingType = embeddableMappingType;
+		this.parentInjectionAttribute = parentInjectionAttribute;
+		this.containingTableExpression = containingTableExpression;
+		this.columnExpressions = columnExpressions;
+		this.sqlAliasStem = sqlAliasStem;
+	}
+
+	@Override
+	public Nature getNature() {
+		return nature;
+	}
+
+	@Override
+	public EmbeddableMappingType getEmbeddableTypeDescriptor() {
+		return embeddableMappingType;
+	}
+
+	@Override
+	public EmbeddableMappingType getPartTypeDescriptor() {
+		return getEmbeddableTypeDescriptor();
+	}
+
+	@Override
+	public String getContainingTableExpression() {
+		return containingTableExpression;
+	}
+
+	@Override
+	public List<String> getMappedColumnExpressions() {
+		return columnExpressions;
+	}
+
+	@Override
+	public SingularAttributeMapping getParentInjectionAttributeMapping() {
+		return parentInjectionAttribute;
+	}
+
+	@Override
+	public String getFetchableName() {
+		return getNature().getName();
+	}
+
+	@Override
+	public FetchStrategy getMappedFetchStrategy() {
+		return FetchStrategy.IMMEDIATE_JOIN;
+	}
+
+	@Override
+	public Fetch generateFetch(
+			FetchParent fetchParent,
+			NavigablePath fetchablePath,
+			FetchTiming fetchTiming,
+			boolean selected,
+			LockMode lockMode,
+			String resultVariable,
+			DomainResultCreationState creationState) {
+		return new CompositeFetch(
+				fetchablePath,
+				this,
+				fetchParent,
+				FetchTiming.IMMEDIATE,
+				false,
+				creationState
+		);
+	}
+
+	@Override
+	public Expression toSqlExpression(
+			TableGroup tableGroup,
+			Clause clause,
+			SqmToSqlAstConverter walker,
+			SqlAstCreationState sqlAstCreationState) {
+		throw new NotYetImplementedFor6Exception( getClass() );
+	}
+
+	@Override
+	public TableGroupJoin createTableGroupJoin(
+			NavigablePath navigablePath,
+			TableGroup lhs,
+			String explicitSourceAlias,
+			JoinType joinType,
+			LockMode lockMode,
+			SqlAliasBaseGenerator aliasBaseGenerator,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext) {
+		throw new NotYetImplementedFor6Exception( getClass() );
+	}
+
+	@Override
+	public void applyTableReferences(
+			SqlAliasBase sqlAliasBase,
+			JoinType baseJoinType,
+			TableReferenceCollector collector,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext) {
+		throw new NotYetImplementedFor6Exception( getClass() );
+	}
+
+	@Override
+	public String getSqlAliasStem() {
+		return sqlAliasStem;
+	}
+
+	@Override
+	public ModelPart findSubPart(String name, EntityMappingType treatTargetType) {
+		return getEmbeddableTypeDescriptor().findSubPart( name, treatTargetType );
+	}
+
+	@Override
+	public void visitSubParts(Consumer<ModelPart> consumer, EntityMappingType treatTargetType) {
+		getEmbeddableTypeDescriptor().visitSubParts( consumer, treatTargetType );
+	}
+
+	@Override
+	public JavaTypeDescriptor getJavaTypeDescriptor() {
+		return getEmbeddableTypeDescriptor().getJavaTypeDescriptor();
+	}
+
+	@Override
+	public int getNumberOfFetchables() {
+		return getEmbeddableTypeDescriptor().getNumberOfAttributeMappings();
+	}
+}

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

@@ -0,0 +1,81 @@
+/*
+ * 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.mapping.internal;
+
+import org.hibernate.LockMode;
+import org.hibernate.NotYetImplementedFor6Exception;
+import org.hibernate.engine.FetchStrategy;
+import org.hibernate.engine.FetchTiming;
+import org.hibernate.metamodel.mapping.CollectionPart;
+import org.hibernate.metamodel.mapping.EntityMappingType;
+import org.hibernate.metamodel.mapping.EntityValuedModelPart;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.results.spi.DomainResultCreationState;
+import org.hibernate.sql.results.spi.Fetch;
+import org.hibernate.sql.results.spi.FetchParent;
+import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
+
+/**
+ * @author Steve Ebersole
+ */
+public class EntityCollectionPart implements CollectionPart, EntityValuedModelPart {
+	private final Nature nature;
+	private final EntityMappingType entityMappingType;
+
+	@SuppressWarnings("WeakerAccess")
+	public EntityCollectionPart(Nature nature, EntityMappingType entityMappingType) {
+		this.nature = nature;
+		this.entityMappingType = entityMappingType;
+	}
+
+	@Override
+	public Nature getNature() {
+		return nature;
+	}
+
+	@Override
+	public EntityMappingType getPartTypeDescriptor() {
+		return getEntityMappingType();
+	}
+
+	@Override
+	public EntityMappingType getEntityMappingType() {
+		return entityMappingType;
+	}
+
+	@Override
+	public JavaTypeDescriptor getJavaTypeDescriptor() {
+		return getEntityMappingType().getJavaTypeDescriptor();
+	}
+
+	@Override
+	public String getFetchableName() {
+		return nature.getName();
+	}
+
+	@Override
+	public FetchStrategy getMappedFetchStrategy() {
+		return FetchStrategy.IMMEDIATE_JOIN;
+	}
+
+	@Override
+	public Fetch generateFetch(
+			FetchParent fetchParent,
+			NavigablePath fetchablePath,
+			FetchTiming fetchTiming,
+			boolean selected,
+			LockMode lockMode,
+			String resultVariable,
+			DomainResultCreationState creationState) {
+		throw new NotYetImplementedFor6Exception( getClass() );
+	}
+
+	@Override
+	public int getNumberOfFetchables() {
+		return entityMappingType.getNumberOfFetchables();
+	}
+}

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

@@ -7,6 +7,10 @@
 package org.hibernate.metamodel.mapping.internal;
 
 import java.io.Serializable;
+import java.util.Iterator;
+import java.util.List;
+import java.util.SortedMap;
+import java.util.SortedSet;
 import java.util.function.Consumer;
 
 import org.hibernate.LockMode;
@@ -16,36 +20,35 @@ import org.hibernate.collection.internal.StandardArraySemantics;
 import org.hibernate.collection.internal.StandardBagSemantics;
 import org.hibernate.collection.internal.StandardIdentifierBagSemantics;
 import org.hibernate.collection.internal.StandardListSemantics;
-import org.hibernate.collection.internal.StandardMapSemantics;
-import org.hibernate.collection.internal.StandardOrderedMapSemantics;
-import org.hibernate.collection.internal.StandardOrderedSetSemantics;
-import org.hibernate.collection.internal.StandardSetSemantics;
-import org.hibernate.collection.internal.StandardSortedMapSemantics;
-import org.hibernate.collection.internal.StandardSortedSetSemantics;
 import org.hibernate.collection.spi.CollectionSemantics;
+import org.hibernate.dialect.Dialect;
 import org.hibernate.engine.FetchStrategy;
 import org.hibernate.engine.FetchStyle;
 import org.hibernate.engine.FetchTiming;
 import org.hibernate.engine.spi.CascadeStyle;
+import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
-import org.hibernate.mapping.Array;
-import org.hibernate.mapping.Bag;
+import org.hibernate.internal.util.collections.CollectionHelper;
 import org.hibernate.mapping.BasicValue;
 import org.hibernate.mapping.Collection;
 import org.hibernate.mapping.Component;
-import org.hibernate.mapping.IdentifierBag;
-import org.hibernate.mapping.List;
-import org.hibernate.mapping.Map;
+import org.hibernate.mapping.IndexedCollection;
+import org.hibernate.mapping.OneToMany;
 import org.hibernate.mapping.PersistentClass;
-import org.hibernate.mapping.PrimitiveArray;
 import org.hibernate.mapping.Property;
-import org.hibernate.mapping.Set;
+import org.hibernate.mapping.Selectable;
+import org.hibernate.mapping.ToOne;
+import org.hibernate.mapping.Value;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.metamodel.mapping.BasicEntityIdentifierMapping;
 import org.hibernate.metamodel.mapping.BasicValuedMapping;
 import org.hibernate.metamodel.mapping.BasicValuedModelPart;
+import org.hibernate.metamodel.mapping.CollectionIdentifierDescriptor;
 import org.hibernate.metamodel.mapping.CollectionMappingType;
+import org.hibernate.metamodel.mapping.CollectionPart;
 import org.hibernate.metamodel.mapping.EmbeddableMappingType;
 import org.hibernate.metamodel.mapping.EntityIdentifierMapping;
+import org.hibernate.metamodel.mapping.ForeignKeyDescriptor;
 import org.hibernate.metamodel.mapping.JdbcMapping;
 import org.hibernate.metamodel.mapping.ManagedMappingType;
 import org.hibernate.metamodel.mapping.MappingType;
@@ -54,15 +57,19 @@ import org.hibernate.metamodel.mapping.PluralAttributeMapping;
 import org.hibernate.metamodel.mapping.StateArrayContributorMetadata;
 import org.hibernate.metamodel.mapping.StateArrayContributorMetadataAccess;
 import org.hibernate.metamodel.model.convert.spi.BasicValueConverter;
+import org.hibernate.metamodel.spi.DomainMetamodel;
 import org.hibernate.metamodel.spi.RuntimeModelCreationContext;
 import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.persister.collection.SQLLoadableCollection;
 import org.hibernate.persister.entity.EntityPersister;
+import org.hibernate.persister.entity.Joinable;
 import org.hibernate.persister.entity.OuterJoinLoadable;
 import org.hibernate.persister.walking.internal.FetchStrategyHelper;
 import org.hibernate.property.access.spi.PropertyAccess;
 import org.hibernate.query.NavigablePath;
 import org.hibernate.query.sqm.sql.SqlExpressionResolver;
 import org.hibernate.sql.ast.Clause;
+import org.hibernate.sql.ast.spi.SqlAliasStemHelper;
 import org.hibernate.sql.ast.spi.SqlSelection;
 import org.hibernate.sql.ast.tree.expression.ColumnReference;
 import org.hibernate.sql.ast.tree.expression.Expression;
@@ -76,6 +83,7 @@ import org.hibernate.sql.results.spi.Fetch;
 import org.hibernate.sql.results.spi.FetchParent;
 import org.hibernate.type.BasicType;
 import org.hibernate.type.CompositeType;
+import org.hibernate.type.Type;
 import org.hibernate.type.descriptor.java.ImmutableMutabilityPlan;
 import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
 import org.hibernate.type.descriptor.java.MutabilityPlan;
@@ -622,75 +630,152 @@ public class MappingModelCreationHelper {
 		final Collection bootValueMapping = (Collection) bootProperty.getValue();
 
 		final RuntimeModelCreationContext creationContext = creationProcess.getCreationContext();
-		final CollectionPersister collectionDescriptor = creationContext.getDomainModel().findCollectionDescriptor( bootValueMapping.getRole() );
+		final SessionFactoryImplementor sessionFactory = creationContext.getSessionFactory();
+		final Dialect dialect = sessionFactory.getJdbcServices().getJdbcEnvironment().getDialect();
+		final DomainMetamodel domainModel = creationContext.getDomainModel();
+
+		final CollectionPersister collectionDescriptor = domainModel.findCollectionDescriptor( bootValueMapping.getRole() );
 		assert collectionDescriptor != null;
 
+		tableExpression = ( (Joinable) collectionDescriptor ).getTableName();
+
+		final String sqlAliasStem = SqlAliasStemHelper.INSTANCE.generateStemFromAttributeName( bootProperty.getName() );
+
 		final CollectionMappingType<?> collectionMappingType;
 		final JavaTypeDescriptorRegistry jtdRegistry = creationContext.getJavaTypeDescriptorRegistry();
 
-		if ( bootValueMapping instanceof Array ) {
-			if ( bootValueMapping instanceof PrimitiveArray ) {
-				throw new NotYetImplementedFor6Exception();
-			}
-			else {
+		final ForeignKeyDescriptor keyDescriptor = interpretKeyDescriptor(
+				bootProperty,
+				bootValueMapping,
+				dialect,
+				creationProcess
+		);
+
+		final CollectionPart elementDescriptor = interpretElement(
+				bootValueMapping,
+				tableExpression,
+				collectionDescriptor,
+				sqlAliasStem,
+				dialect,
+				creationProcess
+		);
+		final CollectionPart indexDescriptor;
+		CollectionIdentifierDescriptor identifierDescriptor = null;
+
+		final CollectionSemantics collectionSemantics = collectionDescriptor.getCollectionSemantics();
+		switch ( collectionSemantics.getCollectionClassification() ) {
+			case ARRAY: {
 				collectionMappingType = new CollectionMappingTypeImpl(
 						jtdRegistry.getDescriptor( Object[].class ),
 						StandardArraySemantics.INSTANCE
 				);
+
+				final BasicValue index = (BasicValue) ( (IndexedCollection) bootValueMapping ).getIndex();
+				indexDescriptor = new BasicValuedCollectionPart(
+						collectionDescriptor,
+						CollectionPart.Nature.INDEX,
+						creationContext.getTypeConfiguration().getBasicTypeForJavaType( Integer.class ),
+						// no converter
+						null,
+						tableExpression,
+						index.getColumnIterator().next().getText( dialect )
+				);
+
+				break;
 			}
-		}
-		else if ( bootValueMapping instanceof Bag ) {
-			collectionMappingType = new CollectionMappingTypeImpl(
-					jtdRegistry.getDescriptor( java.util.Collection.class ),
-					StandardBagSemantics.INSTANCE
-			);
-		}
-		else if ( bootValueMapping instanceof IdentifierBag ) {
-			collectionMappingType = new CollectionMappingTypeImpl(
-					jtdRegistry.getDescriptor( java.util.Collection.class ),
-					StandardIdentifierBagSemantics.INSTANCE
-			);
-		}
-		else if ( bootValueMapping instanceof List ) {
-			collectionMappingType = new CollectionMappingTypeImpl(
-					jtdRegistry.getDescriptor( java.util.List.class ),
-					StandardListSemantics.INSTANCE
-			);
-		}
-		else if ( bootValueMapping instanceof Map ) {
-			if ( bootValueMapping.isSorted() ) {
+			case BAG: {
 				collectionMappingType = new CollectionMappingTypeImpl(
-						jtdRegistry.getDescriptor( java.util.SortedMap.class ),
-						StandardSortedMapSemantics.INSTANCE
+						jtdRegistry.getDescriptor( java.util.Collection.class ),
+						StandardBagSemantics.INSTANCE
+				);
+
+				indexDescriptor = null;
+
+				break;
+			}
+			case IDBAG: {
+				collectionMappingType = new CollectionMappingTypeImpl(
+						jtdRegistry.getDescriptor( java.util.Collection.class ),
+						StandardIdentifierBagSemantics.INSTANCE
+				);
+
+				indexDescriptor = null;
+
+				assert collectionDescriptor instanceof SQLLoadableCollection;
+				final SQLLoadableCollection loadableCollection = (SQLLoadableCollection) collectionDescriptor;
+				final String identifierColumnName = loadableCollection.getIdentifierColumnName();
+				assert identifierColumnName != null;
+
+				identifierDescriptor = new CollectionIdentifierDescriptorImpl(
+						collectionDescriptor,
+						identifierColumnName,
+						(BasicType) loadableCollection.getIdentifierType()
+				);
+
+				break;
+			}
+			case LIST: {
+				final BasicValue index = (BasicValue) ( (IndexedCollection) bootValueMapping ).getIndex();
+
+				indexDescriptor = new BasicValuedCollectionPart(
+						collectionDescriptor,
+						CollectionPart.Nature.INDEX,
+						creationContext.getTypeConfiguration().getBasicTypeForJavaType( Integer.class ),
+						// no converter
+						null,
+						tableExpression,
+						index.getColumnIterator().next().getText( dialect )
+				);
+
+				collectionMappingType = new CollectionMappingTypeImpl(
+						jtdRegistry.getDescriptor( java.util.List.class ),
+						StandardListSemantics.INSTANCE
+				);
+
+				break;
+			}
+			case MAP:
+			case ORDERED_MAP:
+			case SORTED_MAP: {
+				final Class<? extends java.util.Map> mapJavaType = collectionSemantics.getCollectionClassification() == CollectionClassification.SORTED_MAP
+						? SortedMap.class
+						: java.util.Map.class;
+				collectionMappingType = new CollectionMappingTypeImpl(
+						jtdRegistry.getDescriptor( mapJavaType ),
+						collectionSemantics
+				);
+
+				indexDescriptor = interpretMapKey(
+						bootValueMapping,
+						collectionDescriptor,
+						tableExpression,
+						sqlAliasStem,
+						dialect,
+						creationProcess
+				);
+
+				break;
+			}
+			case SET:
+			case ORDERED_SET:
+			case SORTED_SET: {
+				final Class<? extends java.util.Set> setJavaType = collectionSemantics.getCollectionClassification() == CollectionClassification.SORTED_MAP
+						? SortedSet.class
+						: java.util.Set.class;
+				collectionMappingType = new CollectionMappingTypeImpl(
+						jtdRegistry.getDescriptor( setJavaType ),
+						collectionSemantics
+				);
+
+				indexDescriptor = null;
+
+				break;
+			}
+			default: {
+				throw new MappingException(
+						"Unexpected CollectionClassification : " +  collectionSemantics.getCollectionClassification()
 				);
 			}
-			else {
-				collectionMappingType = new CollectionMappingTypeImpl(
-						jtdRegistry.getDescriptor( java.util.Map.class ),
-						bootValueMapping.hasOrder()
-								? StandardOrderedMapSemantics.INSTANCE
-								: StandardMapSemantics.INSTANCE
-				);
-			}
-		}
-		else if ( bootValueMapping instanceof Set ) {
-			if ( bootValueMapping.isSorted() ) {
-				collectionMappingType = new CollectionMappingTypeImpl(
-						jtdRegistry.getDescriptor( java.util.SortedSet.class ),
-						StandardSortedSetSemantics.INSTANCE
-				);
-			}
-			else {
-				collectionMappingType = new CollectionMappingTypeImpl(
-						jtdRegistry.getDescriptor( java.util.Set.class ),
-						bootValueMapping.hasOrder()
-								? StandardOrderedSetSemantics.INSTANCE
-								: StandardSetSemantics.INSTANCE
-				);
-			}
-		}
-		else {
-			throw new MappingException( "Unexpected org.hibernate.mapping.Collection impl : " +  bootValueMapping );
 		}
 
 		final StateArrayContributorMetadata contributorMetadata = new StateArrayContributorMetadata() {
@@ -733,7 +818,7 @@ public class MappingModelCreationHelper {
 		final FetchStyle style = FetchStrategyHelper.determineFetchStyleByMetadata(
 				( (OuterJoinLoadable) declaringType ).getFetchMode( stateArrayPosition ),
 				collectionDescriptor.getCollectionType(),
-				creationContext.getSessionFactory()
+				sessionFactory
 		);
 
 		return new PluralAttributeMappingImpl(
@@ -742,15 +827,15 @@ public class MappingModelCreationHelper {
 				entityMappingType -> contributorMetadata,
 				collectionMappingType,
 				stateArrayPosition,
-				tableExpression,
-				attrColumnExpressions,
-				null,
-				null,
+				keyDescriptor,
+				elementDescriptor,
+				indexDescriptor,
+				identifierDescriptor,
 				new FetchStrategy(
 						FetchStrategyHelper.determineFetchTiming(
 								style,
 								collectionDescriptor.getCollectionType(),
-								creationContext.getSessionFactory()
+								sessionFactory
 						),
 						style
 				),
@@ -760,6 +845,156 @@ public class MappingModelCreationHelper {
 		);
 	}
 
+	private static ForeignKeyDescriptor interpretKeyDescriptor(
+			Property bootProperty,
+			Collection bootValueMapping,
+			Dialect dialect,
+			MappingModelCreationProcess creationProcess) {
+		final Type keyType = bootValueMapping.getKey().getType();
+
+		if ( keyType instanceof BasicType ) {
+			assert bootValueMapping.getKey().getColumnSpan() == 1;
+			return new SimpleForeignKeyDescriptor(
+					bootValueMapping.getKey().getColumnIterator().next().getText( dialect ),
+					(BasicType) keyType
+			);
+		}
+
+		throw new NotYetImplementedFor6Exception(
+				"Support for composite collection foreign-keys not yet implemented: " + bootValueMapping.getRole()
+		);
+	}
+
+	private static CollectionPart interpretMapKey(
+			Collection bootValueMapping,
+			CollectionPersister collectionDescriptor,
+			String tableExpression,
+			String sqlAliasStem,
+			Dialect dialect,
+			MappingModelCreationProcess creationProcess) {
+		assert bootValueMapping instanceof IndexedCollection;
+		final IndexedCollection indexedCollection = (IndexedCollection) bootValueMapping;
+		final Value bootMapKeyDescriptor = indexedCollection.getIndex();
+
+		if ( bootMapKeyDescriptor instanceof BasicValue ) {
+			final BasicValue basicValue = (BasicValue) bootMapKeyDescriptor;
+			return new BasicValuedCollectionPart(
+					collectionDescriptor,
+					CollectionPart.Nature.INDEX,
+					basicValue.resolve().getResolvedBasicType(),
+					basicValue.resolve().getValueConverter(),
+					tableExpression,
+					basicValue.getColumnIterator().next().getText( dialect )
+			);
+		}
+
+		if ( bootMapKeyDescriptor instanceof Component ) {
+			final Component component = (Component) bootMapKeyDescriptor;
+			final CompositeType compositeType = (CompositeType) component.getType();
+
+			final List<String> columnExpressions = CollectionHelper.arrayList( component.getColumnSpan() );
+			final Iterator<Selectable> columnIterator = component.getColumnIterator();
+			while ( columnIterator.hasNext() ) {
+				columnExpressions.add( columnIterator.next().getText( dialect ) );
+			}
+
+			final EmbeddableMappingType mappingType = EmbeddableMappingType.from(
+					component,
+					compositeType,
+					inflightDescriptor -> new EmbeddedCollectionPart(
+							collectionDescriptor,
+							CollectionPart.Nature.INDEX,
+							inflightDescriptor,
+							// parent-injection
+							null,
+							tableExpression,
+							columnExpressions,
+							sqlAliasStem
+					),
+					creationProcess
+			);
+
+			return (CollectionPart) mappingType.getEmbeddedValueMapping();
+		}
+
+		throw new NotYetImplementedFor6Exception(
+				"Support for plural attributes with index type [" + bootMapKeyDescriptor + "] not yet implemented"
+		);
+	}
+
+	private static CollectionPart interpretElement(
+			Collection bootDescriptor,
+			String tableExpression,
+			CollectionPersister collectionDescriptor,
+			String sqlAliasStem,
+			Dialect dialect,
+			MappingModelCreationProcess creationProcess) {
+		final Value element = bootDescriptor.getElement();
+
+		if ( element instanceof BasicValue ) {
+			final BasicValue basicElement = (BasicValue) element;
+			return new BasicValuedCollectionPart(
+					collectionDescriptor,
+					CollectionPart.Nature.ELEMENT,
+					basicElement.resolve().getResolvedBasicType(),
+					basicElement.resolve().getValueConverter(),
+					tableExpression,
+					basicElement.getColumnIterator().next().getText( dialect )
+			);
+		}
+
+		if ( element instanceof Component ) {
+			final Component component = (Component) element;
+			final CompositeType compositeType = (CompositeType) collectionDescriptor.getElementType();
+
+			final List<String> columnExpressions = CollectionHelper.arrayList( component.getColumnSpan() );
+			final Iterator<Selectable> columnIterator = component.getColumnIterator();
+			while ( columnIterator.hasNext() ) {
+				columnExpressions.add( columnIterator.next().getText( dialect ) );
+			}
+
+			final EmbeddableMappingType mappingType = EmbeddableMappingType.from(
+					component,
+					compositeType,
+					embeddableMappingType -> new EmbeddedCollectionPart(
+							collectionDescriptor,
+							CollectionPart.Nature.ELEMENT,
+							embeddableMappingType,
+							// parent-injection
+							null,
+							tableExpression,
+							columnExpressions,
+							sqlAliasStem
+					),
+					creationProcess
+			);
+
+			return (CollectionPart) mappingType.getEmbeddedValueMapping();
+		}
+
+		if ( element instanceof OneToMany || element instanceof ToOne ) {
+			final EntityPersister associatedEntity;
+
+			if ( element instanceof OneToMany ) {
+				associatedEntity = creationProcess.getEntityPersister(
+						( (OneToMany) element ).getReferencedEntityName()
+				);
+			}
+			else {
+				// many-to-many
+				associatedEntity = creationProcess.getEntityPersister(
+						( (ToOne) element ).getReferencedEntityName()
+				);
+			}
+
+			return new EntityCollectionPart( CollectionPart.Nature.ELEMENT, associatedEntity );
+		}
+
+		throw new NotYetImplementedFor6Exception(
+				"Support for plural attributes with element type [" + element + "] not yet implemented"
+		);
+	}
+
 	private static class CollectionMappingTypeImpl implements CollectionMappingType {
 		private final JavaTypeDescriptor collectionJtd;
 		private final CollectionSemantics semantics;
@@ -773,7 +1008,7 @@ public class MappingModelCreationHelper {
 		}
 
 		@Override
-		public CollectionSemantics getCCollectionSemantics() {
+		public CollectionSemantics getCollectionSemantics() {
 			return semantics;
 		}
 

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

@@ -6,12 +6,17 @@
  */
 package org.hibernate.metamodel.mapping.internal;
 
+import java.util.function.Consumer;
+
 import org.hibernate.LockMode;
-import org.hibernate.NotYetImplementedFor6Exception;
 import org.hibernate.engine.FetchStrategy;
 import org.hibernate.engine.FetchTiming;
 import org.hibernate.engine.spi.CascadeStyle;
+import org.hibernate.metamodel.mapping.CollectionIdentifierDescriptor;
 import org.hibernate.metamodel.mapping.CollectionMappingType;
+import org.hibernate.metamodel.mapping.CollectionPart;
+import org.hibernate.metamodel.mapping.EntityMappingType;
+import org.hibernate.metamodel.mapping.ForeignKeyDescriptor;
 import org.hibernate.metamodel.mapping.ManagedMappingType;
 import org.hibernate.metamodel.mapping.ModelPart;
 import org.hibernate.metamodel.mapping.PluralAttributeMapping;
@@ -20,7 +25,18 @@ import org.hibernate.persister.collection.CollectionPersister;
 import org.hibernate.property.access.spi.PropertyAccess;
 import org.hibernate.query.NavigablePath;
 import org.hibernate.query.sqm.sql.SqlAstCreationState;
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
+import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBase;
+import org.hibernate.sql.ast.spi.SqlAliasBaseGenerator;
+import org.hibernate.sql.ast.spi.SqlAliasStemHelper;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
 import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.ast.tree.from.TableGroupBuilder;
+import org.hibernate.sql.ast.tree.from.TableGroupJoin;
+import org.hibernate.sql.ast.tree.from.TableReferenceCollector;
+import org.hibernate.sql.results.internal.domain.collection.DelayedCollectionFetch;
+import org.hibernate.sql.results.internal.domain.collection.EagerCollectionFetch;
 import org.hibernate.sql.results.spi.DomainResultCreationState;
 import org.hibernate.sql.results.spi.Fetch;
 import org.hibernate.sql.results.spi.FetchParent;
@@ -33,17 +49,18 @@ public class PluralAttributeMappingImpl extends AbstractAttributeMapping impleme
 	private final PropertyAccess propertyAccess;
 	private final StateArrayContributorMetadataAccess stateArrayContributorMetadataAccess;
 
+	private final ForeignKeyDescriptor fkDescriptor;
+	private final CollectionPart elementDescriptor;
+	private final CollectionPart indexDescriptor;
+	private final CollectionIdentifierDescriptor identifierDescriptor;
+
 	private final FetchStrategy fetchStrategy;
-
-	private final String tableExpression;
-	private final String[] attrColumnExpressions;
-
-	private final ModelPart elementDescriptor;
-	private final ModelPart indexDescriptor;
-
 	private final CascadeStyle cascadeStyle;
+
 	private final CollectionPersister collectionDescriptor;
 
+	private final String sqlAliasStem;
+
 	@SuppressWarnings("WeakerAccess")
 	public PluralAttributeMappingImpl(
 			String attributeName,
@@ -51,10 +68,10 @@ public class PluralAttributeMappingImpl extends AbstractAttributeMapping impleme
 			StateArrayContributorMetadataAccess stateArrayContributorMetadataAccess,
 			CollectionMappingType collectionMappingType,
 			int stateArrayPosition,
-			String tableExpression,
-			String[] attrColumnExpressions,
-			ModelPart elementDescriptor,
-			ModelPart indexDescriptor,
+			ForeignKeyDescriptor fkDescriptor,
+			CollectionPart elementDescriptor,
+			CollectionPart indexDescriptor,
+			CollectionIdentifierDescriptor identifierDescriptor,
 			FetchStrategy fetchStrategy,
 			CascadeStyle cascadeStyle,
 			ManagedMappingType declaringType,
@@ -63,36 +80,47 @@ public class PluralAttributeMappingImpl extends AbstractAttributeMapping impleme
 		this.propertyAccess = propertyAccess;
 		this.stateArrayContributorMetadataAccess = stateArrayContributorMetadataAccess;
 		this.stateArrayPosition = stateArrayPosition;
-		this.tableExpression = tableExpression;
-		this.attrColumnExpressions = attrColumnExpressions;
+		this.fkDescriptor = fkDescriptor;
 		this.elementDescriptor = elementDescriptor;
 		this.indexDescriptor = indexDescriptor;
+		this.identifierDescriptor = identifierDescriptor;
 		this.fetchStrategy = fetchStrategy;
 		this.cascadeStyle = cascadeStyle;
 		this.collectionDescriptor = collectionDescriptor;
-	}
 
+		this.sqlAliasStem = SqlAliasStemHelper.INSTANCE.generateStemFromAttributeName( attributeName );
+	}
 
 	@Override
 	public CollectionMappingType getMappedTypeDescriptor() {
 		return (CollectionMappingType) super.getMappedTypeDescriptor();
 	}
 
+	@Override
+	public ForeignKeyDescriptor getKeyDescriptor() {
+		return fkDescriptor;
+	}
+
 	@Override
 	public CollectionPersister getCollectionDescriptor() {
 		return collectionDescriptor;
 	}
 
 	@Override
-	public ModelPart getValueDescriptor() {
+	public CollectionPart getElementDescriptor() {
 		return elementDescriptor;
 	}
 
 	@Override
-	public ModelPart getIndexDescriptor() {
+	public CollectionPart getIndexDescriptor() {
 		return indexDescriptor;
 	}
 
+	@Override
+	public CollectionIdentifierDescriptor getIdentifierDescriptor() {
+		return identifierDescriptor;
+	}
+
 	@Override
 	public int getStateArrayPosition() {
 		return stateArrayPosition;
@@ -128,8 +156,119 @@ public class PluralAttributeMappingImpl extends AbstractAttributeMapping impleme
 			String resultVariable,
 			DomainResultCreationState creationState) {
 		final SqlAstCreationState sqlAstCreationState = creationState.getSqlAstCreationState();
-		final TableGroup collectionTableGroup = sqlAstCreationState.getFromClauseAccess().getTableGroup( fetchablePath );
 
-		throw new NotYetImplementedFor6Exception( getClass() );
+		if ( fetchTiming == FetchTiming.IMMEDIATE || selected ) {
+			final TableGroup collectionTableGroup = sqlAstCreationState.getFromClauseAccess().resolveTableGroup(
+					fetchablePath,
+					p -> {
+						final TableGroupJoin tableGroupJoin = createTableGroupJoin(
+								fetchablePath,
+								sqlAstCreationState.getFromClauseAccess().getTableGroup( fetchParent.getNavigablePath() ),
+								null,
+								JoinType.LEFT,
+								lockMode,
+								creationState.getSqlAliasBaseManager(),
+								creationState.getSqlAstCreationState().getSqlExpressionResolver(),
+								creationState.getSqlAstCreationState().getCreationContext()
+						);
+						return tableGroupJoin.getJoinedGroup();
+					}
+			);
+
+			return new EagerCollectionFetch(
+					fetchablePath,
+					this,
+					fkDescriptor.createDomainResult( fetchablePath, collectionTableGroup, creationState ),
+					getAttributeMetadataAccess().resolveAttributeMetadata( null ).isNullable(),
+					fetchParent,
+					creationState
+			);
+		}
+
+
+		return new DelayedCollectionFetch(
+				fetchablePath,
+				this,
+				true,
+				fetchParent
+		);
+	}
+
+	@Override
+	public String getSqlAliasStem() {
+		return sqlAliasStem;
+	}
+
+	@Override
+	public TableGroupJoin createTableGroupJoin(
+			NavigablePath navigablePath,
+			TableGroup lhs,
+			String explicitSourceAlias,
+			JoinType joinType,
+			LockMode lockMode,
+			SqlAliasBaseGenerator aliasBaseGenerator,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext) {
+		final String aliasRoot = explicitSourceAlias == null ? sqlAliasStem : explicitSourceAlias;
+		final SqlAliasBase sqlAliasBase = aliasBaseGenerator.createSqlAliasBase( aliasRoot );
+
+		final TableGroupBuilder tableGroupBuilder = TableGroupBuilder.builder(
+				navigablePath,
+				this,
+				lockMode,
+				sqlAliasBase,
+				creationContext.getSessionFactory()
+		);
+
+		applyTableReferences(
+				sqlAliasBase,
+				joinType,
+				tableGroupBuilder,
+				sqlExpressionResolver,
+				creationContext
+		);
+
+		return new TableGroupJoin( navigablePath, joinType, tableGroupBuilder.build() );
+	}
+
+	@Override
+	public void applyTableReferences(
+			SqlAliasBase sqlAliasBase,
+			JoinType baseJoinType,
+			TableReferenceCollector collector,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext) {
+		getCollectionDescriptor().applyTableReferences( sqlAliasBase, baseJoinType, collector, sqlExpressionResolver, creationContext );
+	}
+
+	@Override
+	public ModelPart findSubPart(String name, EntityMappingType treatTargetType) {
+		final CollectionPart.Nature nature = CollectionPart.Nature.fromName( name );
+		if ( nature == CollectionPart.Nature.ELEMENT ) {
+			return elementDescriptor;
+		}
+		else if ( nature == CollectionPart.Nature.INDEX ) {
+			return indexDescriptor;
+		}
+
+		return null;
+	}
+
+	@Override
+	public void visitSubParts(Consumer<ModelPart> consumer, EntityMappingType treatTargetType) {
+		consumer.accept( elementDescriptor );
+		if ( indexDescriptor != null ) {
+			consumer.accept( indexDescriptor );
+		}
+	}
+
+	@Override
+	public int getNumberOfFetchables() {
+		return indexDescriptor == null ? 1 : 2;
+	}
+
+	@Override
+	public String toString() {
+		return "PluralAttribute(" + getCollectionDescriptor().getRole() + ")";
 	}
 }

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

@@ -0,0 +1,64 @@
+/*
+ * 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.mapping.internal;
+
+import org.hibernate.metamodel.mapping.ForeignKeyDescriptor;
+import org.hibernate.metamodel.mapping.JdbcMapping;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.query.sqm.sql.SqlAstCreationState;
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
+import org.hibernate.sql.ast.spi.SqlSelection;
+import org.hibernate.sql.ast.tree.expression.ColumnReference;
+import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.results.internal.domain.basic.BasicResult;
+import org.hibernate.sql.results.spi.DomainResult;
+import org.hibernate.sql.results.spi.DomainResultCreationState;
+
+/**
+ * @author Steve Ebersole
+ */
+public class SimpleForeignKeyDescriptor implements ForeignKeyDescriptor {
+	private final String keyColumnExpression;
+	private final JdbcMapping jdbcMapping;
+
+	public SimpleForeignKeyDescriptor(String keyColumnExpression, JdbcMapping jdbcMapping) {
+		this.keyColumnExpression = keyColumnExpression;
+		this.jdbcMapping = jdbcMapping;
+	}
+
+	@Override
+	public DomainResult createDomainResult(
+			NavigablePath collectionPath,
+			TableGroup tableGroup,
+			DomainResultCreationState creationState) {
+		final SqlAstCreationState sqlAstCreationState = creationState.getSqlAstCreationState();
+		final SqlExpressionResolver sqlExpressionResolver = sqlAstCreationState.getSqlExpressionResolver();
+		final SqlSelection sqlSelection = sqlExpressionResolver.resolveSqlSelection(
+				sqlExpressionResolver.resolveSqlExpression(
+						SqlExpressionResolver.createColumnReferenceKey(
+								tableGroup.getPrimaryTableReference(),
+								keyColumnExpression
+						),
+						s -> new ColumnReference(
+								tableGroup.getPrimaryTableReference().getIdentificationVariable(),
+								keyColumnExpression,
+								jdbcMapping,
+								creationState.getSqlAstCreationState().getCreationContext().getSessionFactory()
+						)
+				),
+				jdbcMapping.getJavaTypeDescriptor(),
+				sqlAstCreationState.getCreationContext().getDomainModel().getTypeConfiguration()
+		);
+
+		//noinspection unchecked
+		return new BasicResult(
+				sqlSelection.getValuesArrayPosition(),
+				null,
+				jdbcMapping.getJavaTypeDescriptor()
+		);
+	}
+}

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

@@ -7,12 +7,12 @@
 package org.hibernate.metamodel.mapping.internal;
 
 import org.hibernate.LockMode;
+import org.hibernate.NotYetImplementedFor6Exception;
 import org.hibernate.engine.FetchStrategy;
 import org.hibernate.engine.FetchTiming;
 import org.hibernate.metamodel.mapping.EntityMappingType;
 import org.hibernate.metamodel.mapping.EntityValuedModelPart;
 import org.hibernate.metamodel.mapping.ManagedMappingType;
-import org.hibernate.metamodel.mapping.MappingType;
 import org.hibernate.metamodel.mapping.StateArrayContributorMetadataAccess;
 import org.hibernate.property.access.spi.PropertyAccess;
 import org.hibernate.query.NavigablePath;
@@ -29,7 +29,7 @@ public class SingularAssociationAttributeMapping extends AbstractSingularAttribu
 			int stateArrayPosition,
 			StateArrayContributorMetadataAccess attributeMetadataAccess,
 			FetchStrategy mappedFetchStrategy,
-			MappingType type,
+			EntityMappingType type,
 			ManagedMappingType declaringType,
 			PropertyAccess propertyAccess) {
 		super(
@@ -43,9 +43,14 @@ public class SingularAssociationAttributeMapping extends AbstractSingularAttribu
 		);
 	}
 
+	@Override
+	public EntityMappingType getMappedTypeDescriptor() {
+		return (EntityMappingType) super.getMappedTypeDescriptor();
+	}
+
 	@Override
 	public EntityMappingType getEntityMappingType() {
-		return null;
+		return getMappedTypeDescriptor();
 	}
 
 	@Override
@@ -57,6 +62,11 @@ public class SingularAssociationAttributeMapping extends AbstractSingularAttribu
 			LockMode lockMode,
 			String resultVariable,
 			DomainResultCreationState creationState) {
-		return null;
+		throw new NotYetImplementedFor6Exception( getClass() );
+	}
+
+	@Override
+	public int getNumberOfFetchables() {
+		return getEntityMappingType().getNumberOfFetchables();
 	}
 }

hibernate-core/src/main/java/org/hibernate/persister/collection/AbstractCollectionPersister.java

@@ -16,7 +16,6 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Set;
-import java.util.function.Consumer;
 
 import org.hibernate.AssertionFailure;
 import org.hibernate.FetchMode;
@@ -33,6 +32,7 @@ import org.hibernate.cache.spi.entry.CacheEntryStructure;
 import org.hibernate.cache.spi.entry.StructuredCollectionCacheEntry;
 import org.hibernate.cache.spi.entry.StructuredMapCacheEntry;
 import org.hibernate.cache.spi.entry.UnstructuredCacheEntry;
+import org.hibernate.collection.spi.CollectionSemantics;
 import org.hibernate.collection.spi.PersistentCollection;
 import org.hibernate.dialect.Dialect;
 import org.hibernate.engine.jdbc.batch.internal.BasicBatchKey;
@@ -56,6 +56,7 @@ import org.hibernate.internal.util.collections.ArrayHelper;
 import org.hibernate.jdbc.Expectation;
 import org.hibernate.jdbc.Expectations;
 import org.hibernate.loader.collection.CollectionInitializer;
+import org.hibernate.mapping.BasicValue;
 import org.hibernate.mapping.Collection;
 import org.hibernate.mapping.Column;
 import org.hibernate.mapping.Formula;
@@ -64,9 +65,9 @@ import org.hibernate.mapping.IndexedCollection;
 import org.hibernate.mapping.List;
 import org.hibernate.mapping.Selectable;
 import org.hibernate.mapping.Table;
+import org.hibernate.mapping.Value;
 import org.hibernate.metadata.CollectionMetadata;
-import org.hibernate.metamodel.mapping.ModelPart;
-import org.hibernate.metamodel.model.domain.EmbeddableDomainType;
+import org.hibernate.metamodel.model.convert.spi.BasicValueConverter;
 import org.hibernate.metamodel.model.domain.NavigableRole;
 import org.hibernate.persister.entity.EntityPersister;
 import org.hibernate.persister.entity.PropertyMapping;
@@ -84,18 +85,23 @@ import org.hibernate.persister.walking.spi.CompositeCollectionElementDefinition;
 import org.hibernate.persister.walking.spi.CompositionDefinition;
 import org.hibernate.persister.walking.spi.EntityDefinition;
 import org.hibernate.pretty.MessageHelper;
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
 import org.hibernate.sql.Alias;
 import org.hibernate.sql.SelectFragment;
 import org.hibernate.sql.SimpleSelect;
 import org.hibernate.sql.Template;
+import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBase;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
+import org.hibernate.sql.ast.tree.from.TableReference;
+import org.hibernate.sql.ast.tree.from.TableReferenceCollector;
 import org.hibernate.type.AnyType;
 import org.hibernate.type.AssociationType;
+import org.hibernate.type.BasicType;
 import org.hibernate.type.CollectionType;
 import org.hibernate.type.CompositeType;
 import org.hibernate.type.EntityType;
 import org.hibernate.type.Type;
-import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
-import org.hibernate.type.spi.TypeConfiguration;
 
 import org.jboss.logging.Logger;
 
@@ -234,10 +240,26 @@ public abstract class AbstractCollectionPersister
 	private final Comparator comparator;
 
 
+	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+	// "mapping model"
+
+	private final CollectionSemantics collectionSemantics;
+
+	private final BasicValueConverter elementConverter;
+	private final BasicValueConverter indexConverter;
+
+	// temprary
+	private final BasicType convertedElementType;
+	private final BasicType convertedIndexType;
+
 	public AbstractCollectionPersister(
-			Collection collectionBinding,
+			Collection collectionBootDescriptor,
 			CollectionDataAccess cacheAccessStrategy,
 			PersisterCreationContext creationContext) throws MappingException, CacheException {
+		final Value elementBootDescriptor = collectionBootDescriptor.getElement();
+		final Value indexBootDescriptor = collectionBootDescriptor instanceof IndexedCollection
+				? ( (IndexedCollection) collectionBootDescriptor ).getIndex()
+				: null;
 
 		final Database database = creationContext.getMetadata().getDatabase();
 		final JdbcEnvironment jdbcEnvironment = database.getJdbcEnvironment();
@@ -245,7 +267,7 @@ public abstract class AbstractCollectionPersister
 		this.factory = creationContext.getSessionFactory();
 		this.cacheAccessStrategy = cacheAccessStrategy;
 		if ( factory.getSessionFactoryOptions().isStructuredCacheEntriesEnabled() ) {
-			cacheEntryStructure = collectionBinding.isMap()
+			cacheEntryStructure = collectionBootDescriptor.isMap()
 					? StructuredMapCacheEntry.INSTANCE
 					: StructuredCollectionCacheEntry.INSTANCE;
 		}
@@ -255,54 +277,54 @@ public abstract class AbstractCollectionPersister
 
 		dialect = factory.getDialect();
 		sqlExceptionHelper = factory.getSQLExceptionHelper();
-		collectionType = collectionBinding.getCollectionType();
-		navigableRole = new NavigableRole( collectionBinding.getRole() );
-		entityName = collectionBinding.getOwnerEntityName();
+		collectionType = collectionBootDescriptor.getCollectionType();
+		navigableRole = new NavigableRole( collectionBootDescriptor.getRole() );
+		entityName = collectionBootDescriptor.getOwnerEntityName();
 		ownerPersister = factory.getEntityPersister( entityName );
-		queryLoaderName = collectionBinding.getLoaderName();
-		isMutable = collectionBinding.isMutable();
-		mappedByProperty = collectionBinding.getMappedByProperty();
+		queryLoaderName = collectionBootDescriptor.getLoaderName();
+		isMutable = collectionBootDescriptor.isMutable();
+		mappedByProperty = collectionBootDescriptor.getMappedByProperty();
 
-		Table table = collectionBinding.getCollectionTable();
-		fetchMode = collectionBinding.getElement().getFetchMode();
-		elementType = collectionBinding.getElement().getType();
+		Table table = collectionBootDescriptor.getCollectionTable();
+		fetchMode = elementBootDescriptor.getFetchMode();
+		elementType = elementBootDescriptor.getType();
 		// isSet = collectionBinding.isSet();
 		// isSorted = collectionBinding.isSorted();
-		isPrimitiveArray = collectionBinding.isPrimitiveArray();
-		isArray = collectionBinding.isArray();
-		subselectLoadable = collectionBinding.isSubselectLoadable();
+		isPrimitiveArray = collectionBootDescriptor.isPrimitiveArray();
+		isArray = collectionBootDescriptor.isArray();
+		subselectLoadable = collectionBootDescriptor.isSubselectLoadable();
 
 		qualifiedTableName = determineTableName( table, jdbcEnvironment );
 
-		int spacesSize = 1 + collectionBinding.getSynchronizedTables().size();
+		int spacesSize = 1 + collectionBootDescriptor.getSynchronizedTables().size();
 		spaces = new String[spacesSize];
 		spaces[0] = qualifiedTableName;
-		Iterator iter = collectionBinding.getSynchronizedTables().iterator();
+		Iterator iter = collectionBootDescriptor.getSynchronizedTables().iterator();
 		for ( int i = 1; i < spacesSize; i++ ) {
 			spaces[i] = (String) iter.next();
 		}
 
-		sqlWhereString = StringHelper.isNotEmpty( collectionBinding.getWhere() ) ? "( " + collectionBinding.getWhere() + ") " : null;
+		sqlWhereString = StringHelper.isNotEmpty( collectionBootDescriptor.getWhere() ) ? "( " + collectionBootDescriptor.getWhere() + ") " : null;
 		hasWhere = sqlWhereString != null;
 		sqlWhereStringTemplate = hasWhere ?
 				Template.renderWhereStringTemplate( sqlWhereString, dialect, factory.getSqlFunctionRegistry() ) :
 				null;
 
-		hasOrphanDelete = collectionBinding.hasOrphanDelete();
+		hasOrphanDelete = collectionBootDescriptor.hasOrphanDelete();
 
-		int batch = collectionBinding.getBatchSize();
+		int batch = collectionBootDescriptor.getBatchSize();
 		if ( batch == -1 ) {
 			batch = factory.getSessionFactoryOptions().getDefaultBatchFetchSize();
 		}
 		batchSize = batch;
 
-		isVersioned = collectionBinding.isOptimisticLocked();
+		isVersioned = collectionBootDescriptor.isOptimisticLocked();
 
 		// KEY
 
-		keyType = collectionBinding.getKey().getType();
-		iter = collectionBinding.getKey().getColumnIterator();
-		int keySpan = collectionBinding.getKey().getColumnSpan();
+		keyType = collectionBootDescriptor.getKey().getType();
+		iter = collectionBootDescriptor.getKey().getColumnIterator();
+		int keySpan = collectionBootDescriptor.getKey().getColumnSpan();
 		keyColumnNames = new String[keySpan];
 		keyColumnAliases = new String[keySpan];
 		int k = 0;
@@ -328,7 +350,7 @@ public abstract class AbstractCollectionPersister
 			elementPersister = null;
 		}
 
-		int elementSpan = collectionBinding.getElement().getColumnSpan();
+		int elementSpan = elementBootDescriptor.getColumnSpan();
 		elementColumnAliases = new String[elementSpan];
 		elementColumnNames = new String[elementSpan];
 		elementColumnWriters = new String[elementSpan];
@@ -341,13 +363,13 @@ public abstract class AbstractCollectionPersister
 		elementColumnIsInPrimaryKey = new boolean[elementSpan];
 		boolean isPureFormula = true;
 		boolean hasNotNullableColumns = false;
-		boolean oneToMany = collectionBinding.isOneToMany();
+		boolean oneToMany = collectionBootDescriptor.isOneToMany();
 		boolean[] columnInsertability = null;
 		if ( !oneToMany ) {
-			columnInsertability = collectionBinding.getElement().getColumnInsertability();
+			columnInsertability = elementBootDescriptor.getColumnInsertability();
 		}
 		int j = 0;
-		iter = collectionBinding.getElement().getColumnIterator();
+		iter = elementBootDescriptor.getColumnIterator();
 		while ( iter.hasNext() ) {
 			Selectable selectable = (Selectable) iter.next();
 			elementColumnAliases[j] = selectable.getAlias( dialect, table );
@@ -390,10 +412,10 @@ public abstract class AbstractCollectionPersister
 
 		// INDEX AND ROW SELECT
 
-		hasIndex = collectionBinding.isIndexed();
+		hasIndex = collectionBootDescriptor.isIndexed();
 		if ( hasIndex ) {
 			// NativeSQL: collect index column and auto-aliases
-			IndexedCollection indexedCollection = (IndexedCollection) collectionBinding;
+			IndexedCollection indexedCollection = (IndexedCollection) collectionBootDescriptor;
 			indexType = indexedCollection.getIndex().getType();
 			int indexSpan = indexedCollection.getIndex().getColumnSpan();
 			boolean[] indexColumnInsertability = indexedCollection.getIndex().getColumnInsertability();
@@ -440,12 +462,12 @@ public abstract class AbstractCollectionPersister
 			baseIndex = 0;
 		}
 
-		hasIdentifier = collectionBinding.isIdentified();
+		hasIdentifier = collectionBootDescriptor.isIdentified();
 		if ( hasIdentifier ) {
-			if ( collectionBinding.isOneToMany() ) {
+			if ( collectionBootDescriptor.isOneToMany() ) {
 				throw new MappingException( "one-to-many collections with identifiers are not supported" );
 			}
-			IdentifierCollection idColl = (IdentifierCollection) collectionBinding;
+			IdentifierCollection idColl = (IdentifierCollection) collectionBootDescriptor;
 			identifierType = idColl.getIdentifier().getType();
 			iter = idColl.getIdentifier().getColumnIterator();
 			Column col = (Column) iter.next();
@@ -473,68 +495,68 @@ public abstract class AbstractCollectionPersister
 		// sqlSelectString = sqlSelectString();
 		// sqlSelectRowString = sqlSelectRowString();
 
-		if ( collectionBinding.getCustomSQLInsert() == null ) {
+		if ( collectionBootDescriptor.getCustomSQLInsert() == null ) {
 			sqlInsertRowString = generateInsertRowString();
 			insertCallable = false;
 			insertCheckStyle = ExecuteUpdateResultCheckStyle.COUNT;
 		}
 		else {
-			sqlInsertRowString = collectionBinding.getCustomSQLInsert();
-			insertCallable = collectionBinding.isCustomInsertCallable();
-			insertCheckStyle = collectionBinding.getCustomSQLInsertCheckStyle() == null
-					? ExecuteUpdateResultCheckStyle.determineDefault( collectionBinding.getCustomSQLInsert(), insertCallable )
-					: collectionBinding.getCustomSQLInsertCheckStyle();
+			sqlInsertRowString = collectionBootDescriptor.getCustomSQLInsert();
+			insertCallable = collectionBootDescriptor.isCustomInsertCallable();
+			insertCheckStyle = collectionBootDescriptor.getCustomSQLInsertCheckStyle() == null
+					? ExecuteUpdateResultCheckStyle.determineDefault( collectionBootDescriptor.getCustomSQLInsert(), insertCallable )
+					: collectionBootDescriptor.getCustomSQLInsertCheckStyle();
 		}
 
-		if ( collectionBinding.getCustomSQLUpdate() == null ) {
+		if ( collectionBootDescriptor.getCustomSQLUpdate() == null ) {
 			sqlUpdateRowString = generateUpdateRowString();
 			updateCallable = false;
 			updateCheckStyle = ExecuteUpdateResultCheckStyle.COUNT;
 		}
 		else {
-			sqlUpdateRowString = collectionBinding.getCustomSQLUpdate();
-			updateCallable = collectionBinding.isCustomUpdateCallable();
-			updateCheckStyle = collectionBinding.getCustomSQLUpdateCheckStyle() == null
-					? ExecuteUpdateResultCheckStyle.determineDefault( collectionBinding.getCustomSQLUpdate(), insertCallable )
-					: collectionBinding.getCustomSQLUpdateCheckStyle();
+			sqlUpdateRowString = collectionBootDescriptor.getCustomSQLUpdate();
+			updateCallable = collectionBootDescriptor.isCustomUpdateCallable();
+			updateCheckStyle = collectionBootDescriptor.getCustomSQLUpdateCheckStyle() == null
+					? ExecuteUpdateResultCheckStyle.determineDefault( collectionBootDescriptor.getCustomSQLUpdate(), insertCallable )
+					: collectionBootDescriptor.getCustomSQLUpdateCheckStyle();
 		}
 
-		if ( collectionBinding.getCustomSQLDelete() == null ) {
+		if ( collectionBootDescriptor.getCustomSQLDelete() == null ) {
 			sqlDeleteRowString = generateDeleteRowString();
 			deleteCallable = false;
 			deleteCheckStyle = ExecuteUpdateResultCheckStyle.NONE;
 		}
 		else {
-			sqlDeleteRowString = collectionBinding.getCustomSQLDelete();
-			deleteCallable = collectionBinding.isCustomDeleteCallable();
+			sqlDeleteRowString = collectionBootDescriptor.getCustomSQLDelete();
+			deleteCallable = collectionBootDescriptor.isCustomDeleteCallable();
 			deleteCheckStyle = ExecuteUpdateResultCheckStyle.NONE;
 		}
 
-		if ( collectionBinding.getCustomSQLDeleteAll() == null ) {
+		if ( collectionBootDescriptor.getCustomSQLDeleteAll() == null ) {
 			sqlDeleteString = generateDeleteString();
 			deleteAllCallable = false;
 			deleteAllCheckStyle = ExecuteUpdateResultCheckStyle.NONE;
 		}
 		else {
-			sqlDeleteString = collectionBinding.getCustomSQLDeleteAll();
-			deleteAllCallable = collectionBinding.isCustomDeleteAllCallable();
+			sqlDeleteString = collectionBootDescriptor.getCustomSQLDeleteAll();
+			deleteAllCallable = collectionBootDescriptor.isCustomDeleteAllCallable();
 			deleteAllCheckStyle = ExecuteUpdateResultCheckStyle.NONE;
 		}
 
-		sqlSelectSizeString = generateSelectSizeString( collectionBinding.isIndexed() && !collectionBinding.isMap() );
+		sqlSelectSizeString = generateSelectSizeString( collectionBootDescriptor.isIndexed() && !collectionBootDescriptor.isMap() );
 		sqlDetectRowByIndexString = generateDetectRowByIndexString();
 		sqlDetectRowByElementString = generateDetectRowByElementString();
 		sqlSelectRowByIndexString = generateSelectRowByIndexString();
 
 		logStaticSQL();
 
-		isLazy = collectionBinding.isLazy();
-		isExtraLazy = collectionBinding.isExtraLazy();
+		isLazy = collectionBootDescriptor.isLazy();
+		isExtraLazy = collectionBootDescriptor.isExtraLazy();
 
-		isInverse = collectionBinding.isInverse();
+		isInverse = collectionBootDescriptor.isInverse();
 
-		if ( collectionBinding.isArray() ) {
-			elementClass = ( (org.hibernate.mapping.Array) collectionBinding ).getElementClass();
+		if ( collectionBootDescriptor.isArray() ) {
+			elementClass = ( (org.hibernate.mapping.Array) collectionBootDescriptor ).getElementClass();
 		}
 		else {
 			// for non-arrays, we don't need to know the element class
@@ -569,9 +591,9 @@ public abstract class AbstractCollectionPersister
 			}
 		}
 
-		hasOrder = collectionBinding.getOrderBy() != null;
+		hasOrder = collectionBootDescriptor.getOrderBy() != null;
 		if ( hasOrder ) {
-			LOG.debugf( "Translating order-by fragment [%s] for collection role : %s",  collectionBinding.getOrderBy(), getRole() );
+			LOG.debugf( "Translating order-by fragment [%s] for collection role : %s",  collectionBootDescriptor.getOrderBy(), getRole() );
 //			orderByTranslation = Template.translateOrderBy(
 //					collectionBinding.getOrderBy(),
 //					new ColumnMapperImpl(),
@@ -587,20 +609,20 @@ public abstract class AbstractCollectionPersister
 		}
 
 		// Handle any filters applied to this collectionBinding
-		filterHelper = new FilterHelper( collectionBinding.getFilters(), factory);
+		filterHelper = new FilterHelper( collectionBootDescriptor.getFilters(), factory);
 
 		// Handle any filters applied to this collectionBinding for many-to-many
-		manyToManyFilterHelper = new FilterHelper( collectionBinding.getManyToManyFilters(), factory);
-		manyToManyWhereString = StringHelper.isNotEmpty( collectionBinding.getManyToManyWhere() ) ?
-				"( " + collectionBinding.getManyToManyWhere() + ")" :
+		manyToManyFilterHelper = new FilterHelper( collectionBootDescriptor.getManyToManyFilters(), factory);
+		manyToManyWhereString = StringHelper.isNotEmpty( collectionBootDescriptor.getManyToManyWhere() ) ?
+				"( " + collectionBootDescriptor.getManyToManyWhere() + ")" :
 				null;
 		manyToManyWhereTemplate = manyToManyWhereString == null ?
 				null :
 				Template.renderWhereStringTemplate( manyToManyWhereString, factory.getDialect(), factory.getSqlFunctionRegistry() );
 
-		hasManyToManyOrder = collectionBinding.getManyToManyOrdering() != null;
+		hasManyToManyOrder = collectionBootDescriptor.getManyToManyOrdering() != null;
 		if ( hasManyToManyOrder ) {
-			LOG.debugf( "Translating many-to-many order-by fragment [%s] for collection role : %s",  collectionBinding.getOrderBy(), getRole() );
+			LOG.debugf( "Translating many-to-many order-by fragment [%s] for collection role : %s",  collectionBootDescriptor.getOrderBy(), getRole() );
 //			manyToManyOrderByTranslation = Template.translateOrderBy(
 //					collectionBinding.getManyToManyOrdering(),
 //					new ColumnMapperImpl(),
@@ -614,9 +636,37 @@ public abstract class AbstractCollectionPersister
 //			manyToManyOrderByTranslation = null;
 		}
 
-		comparator = collectionBinding.getComparator();
+		comparator = collectionBootDescriptor.getComparator();
 
 		initCollectionPropertyMap();
+
+		// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+		// "mapping model"
+
+		this.collectionSemantics = creationContext.getBootstrapContext()
+				.getMetadataBuildingOptions()
+				.getPersistentCollectionRepresentationResolver()
+				.resolveRepresentation( collectionBootDescriptor );
+
+		if ( elementBootDescriptor instanceof BasicValue ) {
+			final BasicValue.Resolution<?> basicTypeResolution = ( (BasicValue) elementBootDescriptor ).resolve();
+			this.elementConverter = basicTypeResolution.getValueConverter();
+			this.convertedElementType = basicTypeResolution.getResolvedBasicType();
+		}
+		else {
+			this.elementConverter = null;
+			this.convertedElementType = null;
+		}
+
+		if ( indexBootDescriptor instanceof BasicValue ) {
+			final BasicValue.Resolution<?> basicTypeResolution = ( (BasicValue) indexBootDescriptor ).resolve();
+			this.indexConverter = basicTypeResolution.getValueConverter();
+			this.convertedIndexType = basicTypeResolution.getResolvedBasicType();
+		}
+		else {
+			this.indexConverter = null;
+			this.convertedIndexType = null;
+		}
 	}
 
 	@Override
@@ -872,6 +922,16 @@ public abstract class AbstractCollectionPersister
 		return elementType;
 	}
 
+	@Override
+	public BasicValueConverter getElementConverter() {
+		return elementConverter;
+	}
+
+	@Override
+	public BasicValueConverter getIndexConverter() {
+		return indexConverter;
+	}
+
 	/**
 	 * Return the element class of an array, or null otherwise.  needed by arrays
 	 */
@@ -947,7 +1007,14 @@ public abstract class AbstractCollectionPersister
 	 */
 	protected int writeElement(PreparedStatement st, Object elt, int i, SharedSessionContractImplementor session)
 			throws HibernateException, SQLException {
-		getElementType().nullSafeSet( st, elt, i, elementColumnIsSettable, session );
+		if ( elementConverter != null ) {
+			//noinspection unchecked
+			final Object converted = elementConverter.toRelationalValue( elt );
+			convertedElementType.getJdbcValueBinder().bind( st, converted, i, session );
+		}
+		else {
+			getElementType().nullSafeSet( st, elt, i, elementColumnIsSettable, session );
+		}
 		return i + ArrayHelper.countTrue( elementColumnIsSettable );
 
 	}
@@ -957,7 +1024,16 @@ public abstract class AbstractCollectionPersister
 	 */
 	protected int writeIndex(PreparedStatement st, Object index, int i, SharedSessionContractImplementor session)
 			throws HibernateException, SQLException {
-		getIndexType().nullSafeSet( st, incrementIndexByBase( index ), i, indexColumnIsSettable, session );
+		if ( indexConverter != null ) {
+			//noinspection unchecked
+			final Object converted = indexConverter.toRelationalValue( index );
+			//noinspection unchecked
+			convertedIndexType.getJdbcValueBinder().bind( st, converted, i, session );
+		}
+		else {
+			getIndexType().nullSafeSet( st, incrementIndexByBase( index ), i, indexColumnIsSettable, session );
+		}
+
 		return i + ArrayHelper.countTrue( indexColumnIsSettable );
 	}
 
@@ -976,7 +1052,13 @@ public abstract class AbstractCollectionPersister
 		if ( elementIsPureFormula ) {
 			throw new AssertionFailure( "cannot use a formula-based element in the where condition" );
 		}
-		getElementType().nullSafeSet( st, elt, i, elementColumnIsInPrimaryKey, session );
+		if ( elementConverter != null ) {
+			final Object converted = elementConverter.toRelationalValue( elt );
+			convertedElementType.getJdbcValueBinder().bind( st, converted, i, session );
+		}
+		else {
+			getElementType().nullSafeSet( st, elt, i, elementColumnIsInPrimaryKey, session );
+		}
 		return i + elementColumnAliases.length;
 
 	}
@@ -989,7 +1071,13 @@ public abstract class AbstractCollectionPersister
 		if ( indexContainsFormula ) {
 			throw new AssertionFailure( "cannot use a formula-based index in the where condition" );
 		}
-		getIndexType().nullSafeSet( st, incrementIndexByBase( index ), i, session );
+		if ( indexConverter != null ) {
+			final Object converted = indexConverter.toRelationalValue( index );
+			convertedIndexType.getJdbcValueBinder().bind( st, converted, i, session );
+		}
+		else {
+			getIndexType().nullSafeSet( st, incrementIndexByBase( index ), i, session );
+		}
 		return i + indexColumnAliases.length;
 	}
 
@@ -2297,4 +2385,51 @@ public abstract class AbstractCollectionPersister
 			}
 		};
 	}
+
+
+	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+	// "mapping model"
+
+
+	@Override
+	public void applyTableReferences(
+			SqlAliasBase sqlAliasBase,
+			JoinType baseJoinType,
+			TableReferenceCollector collector,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext) {
+		if ( isOneToMany() ) {
+			// one-to-many does not define a "collection table"
+			assert elementPersister != null;
+		}
+		else {
+			// we do have a "collection table" - apply it first
+			collector.applySecondaryTableReferences(
+					new TableReference( qualifiedTableName, sqlAliasBase.generateNewAlias(), false, getFactory() ),
+					baseJoinType,
+					(lhs, rhs, joinType) -> {
+						// create the join-predicate between the owner table and the collection table
+						throw new NotYetImplementedFor6Exception( getClass() );
+					}
+			);
+
+		}
+
+		if ( elementPersister != null ) {
+			elementPersister.applyTableReferences(
+					sqlAliasBase,
+					// todo (6.0) : determine the proper join-type to use
+					JoinType.LEFT,
+					collector,
+					sqlExpressionResolver,
+					creationContext
+			);
+		}
+
+	}
+
+	@Override
+	public CollectionSemantics getCollectionSemantics() {
+		return collectionSemantics;
+	}
 }

hibernate-core/src/main/java/org/hibernate/persister/collection/BasicCollectionPersister.java

@@ -32,6 +32,7 @@ import org.hibernate.loader.collection.BatchingCollectionInitializerBuilder;
 import org.hibernate.loader.collection.CollectionInitializer;
 import org.hibernate.loader.collection.SubselectCollectionLoader;
 import org.hibernate.mapping.Collection;
+import org.hibernate.metamodel.model.convert.spi.BasicValueConverter;
 import org.hibernate.persister.entity.Joinable;
 import org.hibernate.persister.spi.PersisterCreationContext;
 import org.hibernate.pretty.MessageHelper;

hibernate-core/src/main/java/org/hibernate/persister/collection/CollectionPersister.java

@@ -14,17 +14,26 @@ import java.util.Map;
 
 import org.hibernate.HibernateException;
 import org.hibernate.MappingException;
+import org.hibernate.NotYetImplementedFor6Exception;
 import org.hibernate.cache.spi.access.CollectionDataAccess;
 import org.hibernate.cache.spi.entry.CacheEntryStructure;
+import org.hibernate.collection.spi.CollectionSemantics;
 import org.hibernate.collection.spi.PersistentCollection;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.metadata.CollectionMetadata;
 import org.hibernate.metamodel.CollectionClassification;
+import org.hibernate.metamodel.model.convert.spi.BasicValueConverter;
 import org.hibernate.metamodel.model.domain.NavigableRole;
 import org.hibernate.persister.entity.EntityPersister;
 import org.hibernate.persister.walking.spi.CollectionDefinition;
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
+import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBase;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
+import org.hibernate.sql.ast.tree.from.TableReferenceCollector;
+import org.hibernate.sql.ast.tree.from.TableReferenceContributor;
 import org.hibernate.type.CollectionType;
 import org.hibernate.type.Type;
 
@@ -62,7 +71,7 @@ import org.hibernate.type.Type;
  * @see org.hibernate.collection.spi.PersistentCollection
  * @author Gavin King
  */
-public interface CollectionPersister extends CollectionDefinition {
+public interface CollectionPersister extends CollectionDefinition, TableReferenceContributor {
 	/**
 	 * Initialize the given collection with the given key
 	 * TODO: add owner argument!!
@@ -103,6 +112,21 @@ public interface CollectionPersister extends CollectionDefinition {
 	 * Return the element class of an array, or null otherwise
 	 */
 	Class getElementClass();
+
+	/**
+	 * The value converter for the element values of this collection
+	 */
+	default BasicValueConverter getElementConverter() {
+		return null;
+	}
+
+	/**
+	 * The value converter for index values of this collection (effectively map keys only)
+	 */
+	default BasicValueConverter getIndexConverter() {
+		return null;
+	}
+
 	/**
 	 * Read the key from a row of the JDBC <tt>ResultSet</tt>
 	 */
@@ -332,4 +356,30 @@ public interface CollectionPersister extends CollectionDefinition {
 	 * @see CollectionClassification#SORTED_SET
 	 */
 	Comparator<?> getSortingComparator();
+
+
+	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+	// mapping model
+
+	@Override
+	default void applyTableReferences(
+			SqlAliasBase sqlAliasBase,
+			JoinType baseJoinType,
+			TableReferenceCollector collector,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext) {
+		throw new NotYetImplementedFor6Exception(
+				"The persister used for this collection [" + getNavigableRole()
+						+ "] does not yet implement support for use in SQL AST creation;"
+						+ " should implement `TableReferenceContributor#applyTableReferences`"
+		);
+	}
+
+	default CollectionSemantics getCollectionSemantics() {
+		throw new NotYetImplementedFor6Exception(
+				"The persister used for this collection [" + getNavigableRole()
+						+ "] does not yet implement support for `"
+						+ CollectionSemantics.class.getName() + "`"
+		);
+	}
 }

hibernate-core/src/main/java/org/hibernate/persister/entity/AbstractEntityPersister.java

@@ -184,7 +184,9 @@ import org.hibernate.sql.ast.tree.expression.Expression;
 import org.hibernate.sql.ast.tree.expression.QueryLiteral;
 import org.hibernate.sql.ast.tree.from.StandardTableGroup;
 import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.ast.tree.from.TableGroupBuilder;
 import org.hibernate.sql.ast.tree.from.TableReference;
+import org.hibernate.sql.ast.tree.from.TableReferenceCollector;
 import org.hibernate.sql.ast.tree.from.TableReferenceJoin;
 import org.hibernate.sql.ast.tree.predicate.ComparisonPredicate;
 import org.hibernate.sql.ast.tree.predicate.Junction;
@@ -1187,20 +1189,23 @@ public abstract class AbstractEntityPersister
 			SqlAstCreationContext creationContext) {
 		final SqlAliasBase sqlAliasBase = aliasBaseGenerator.createSqlAliasBase( getSqlAliasStem() );
 
-		final TableReference primaryTableReference = resolvePrimaryTableReference( sqlAliasBase, sqlExpressionResolver );
-
-		final List<TableReferenceJoin> joins = new ArrayList<>(  );
-		resolveTableReferenceJoins( primaryTableReference, sqlAliasBase, tableReferenceJoinType, joins::add, sqlExpressionResolver );
-
-		return new StandardTableGroup(
+		final TableGroupBuilder builder = TableGroupBuilder.builder(
 				navigablePath,
 				this,
 				lockMode,
-				primaryTableReference,
-				joins,
 				sqlAliasBase,
-				getFactory()
+				creationContext.getSessionFactory()
 		);
+
+		applyTableReferences(
+				sqlAliasBase,
+				tableReferenceJoinType,
+				builder,
+				sqlExpressionResolver,
+				creationContext
+		);
+
+		return builder.build();
 	}
 
 	protected TableReference resolvePrimaryTableReference(
@@ -1228,6 +1233,33 @@ public abstract class AbstractEntityPersister
 		}
 	}
 
+	@Override
+	public void applyTableReferences(
+			SqlAliasBase sqlAliasBase,
+			org.hibernate.sql.ast.JoinType baseJoinType,
+			TableReferenceCollector collector,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext) {
+		final TableReference primaryTableReference = resolvePrimaryTableReference(
+				sqlAliasBase,
+				sqlExpressionResolver
+		);
+
+		collector.applyPrimaryReference( primaryTableReference );
+
+		for ( int i = 1; i < getSubclassTableSpan(); i++ ) {
+			collector.addTableReferenceJoin(
+					createTableReferenceJoin(
+							i,
+							primaryTableReference,
+							baseJoinType,
+							sqlAliasBase,
+							sqlExpressionResolver
+					)
+			);
+		}
+	}
+
 	protected TableReferenceJoin createTableReferenceJoin(
 			int subClassTablePosition,
 			TableReference rootTableReference,
@@ -6483,6 +6515,11 @@ public abstract class AbstractEntityPersister
 		// otherwise, nothing to do
 	}
 
+	@Override
+	public int getNumberOfFetchables() {
+		return attributeMappings.size();
+	}
+
 	@Override
 	public void visitFetchables(
 			Consumer<Fetchable> fetchableConsumer,

hibernate-core/src/main/java/org/hibernate/persister/entity/EntityPersister.java

@@ -38,8 +38,13 @@ import org.hibernate.metamodel.model.domain.NavigableRole;
 import org.hibernate.metamodel.spi.EntityRepresentationStrategy;
 import org.hibernate.persister.walking.spi.EntityDefinition;
 import org.hibernate.query.sqm.mutation.spi.SqmMultiTableMutationStrategy;
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
+import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBase;
 import org.hibernate.sql.ast.spi.SqlAliasStemHelper;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
 import org.hibernate.sql.ast.tree.from.RootTableGroupProducer;
+import org.hibernate.sql.ast.tree.from.TableReferenceCollector;
 import org.hibernate.tuple.entity.EntityMetamodel;
 import org.hibernate.tuple.entity.EntityTuplizer;
 import org.hibernate.type.Type;
@@ -93,6 +98,11 @@ public interface EntityPersister extends EntityDefinition, EntityValuedModelPart
 	@Deprecated
 	void generateEntityDefinition();
 
+	@Override
+	default int getNumberOfFetchables() {
+		return getNumberOfAttributeMappings();
+	}
+
 	/**
 	 * Finish the initialization of this object. {@link #prepareMappingModel}
 	 * must be called for all entity persisters before calling this method.
@@ -906,6 +916,4 @@ public interface EntityPersister extends EntityDefinition, EntityValuedModelPart
 	default boolean canIdentityInsertBeDelayed() {
 		return false;
 	}
-
-
 }

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

@@ -499,6 +499,7 @@ public abstract class BaseSqmToSqlAstConverter
 				creationContext
 		);
 
+		lhsTableGroup.addTableGroupJoin( tableGroupJoin );
 		fromClauseIndex.register( sqmJoin, tableGroupJoin.getJoinedGroup() );
 
 		// add any additional join restrictions

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

@@ -37,7 +37,6 @@ public class FromClauseIndex extends SimpleFromClauseAccessImpl {
 	 * Holds *explicitly* fetched joins
 	 */
 	private Map<NavigablePath, SqmAttributeJoin> fetchesByPath;
-	private Map<NavigablePath, Map<NavigablePath, SqmAttributeJoin>> fetchesByParentPath;
 
 	private final Set<String> affectedTableNames = new HashSet<>();
 
@@ -61,6 +60,20 @@ public class FromClauseIndex extends SimpleFromClauseAccessImpl {
 				);
 			}
 		}
+
+		if ( sqmPath instanceof SqmAttributeJoin ) {
+			final SqmAttributeJoin sqmJoin = (SqmAttributeJoin) sqmPath;
+			if ( sqmJoin.isFetched() ) {
+				registerJoinFetch( sqmJoin );
+			}
+		}
+	}
+
+	private void registerJoinFetch(SqmAttributeJoin sqmJoin) {
+		if ( fetchesByPath == null ) {
+			fetchesByPath = new HashMap<>();
+		}
+		fetchesByPath.put( sqmJoin.getNavigablePath(), sqmJoin );
 	}
 
 	public boolean isResolved(SqmFrom fromElement) {

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

@@ -31,6 +31,7 @@ import org.hibernate.query.spi.QueryParameterBindings;
 import org.hibernate.query.sqm.internal.DomainParameterXref;
 import org.hibernate.query.sqm.sql.BaseSqmToSqlAstConverter;
 import org.hibernate.query.sqm.sql.SqlAstCreationState;
+import org.hibernate.query.sqm.sql.SqmSelectToSqlAstConverter;
 import org.hibernate.query.sqm.tree.expression.SqmLiteralEntityType;
 import org.hibernate.query.sqm.tree.from.SqmAttributeJoin;
 import org.hibernate.query.sqm.tree.select.SqmDynamicInstantiation;
@@ -67,7 +68,7 @@ import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
 @SuppressWarnings("unchecked")
 public class StandardSqmSelectToSqlAstConverter
 		extends BaseSqmToSqlAstConverter
-		implements DomainResultCreationState, org.hibernate.query.sqm.sql.SqmSelectToSqlAstConverter {
+		implements DomainResultCreationState, SqmSelectToSqlAstConverter {
 	private final LoadQueryInfluencers fetchInfluencers;
 	private final CircularFetchDetector circularFetchDetector = new CircularFetchDetector();
 
@@ -155,7 +156,7 @@ public class StandardSqmSelectToSqlAstConverter
 
 	@Override
 	public List<Fetch> visitFetches(FetchParent fetchParent) {
-		final List<Fetch> fetches = CollectionHelper.arrayList( fetchParent.getReferencedMappingType().getNumberOfAttributeMappings() );
+		final List<Fetch> fetches = CollectionHelper.arrayList( fetchParent.getReferencedMappingType().getNumberOfFetchables() );
 
 		//noinspection Convert2Lambda
 		final Consumer<Fetchable> fetchableConsumer = new Consumer<Fetchable>() {
@@ -214,7 +215,7 @@ public class StandardSqmSelectToSqlAstConverter
 
 		if ( fetchedJoin != null ) {
 			// there was an explicit fetch in the SQM
-			//		there should be a TableGroupJoin registered n SqmJoin registered for this `fetchablePath` already
+			//		there should be a TableGroupJoin registered for this `fetchablePath` already
 			//		because it
 			assert getFromClauseIndex().getTableGroup( fetchablePath ) != null;
 

hibernate-core/src/main/java/org/hibernate/sql/ast/tree/from/StandardTableGroup.java

@@ -6,13 +6,18 @@
  */
 package org.hibernate.sql.ast.tree.from;
 
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
+import java.util.function.BiFunction;
 import java.util.function.Consumer;
 
 import org.hibernate.LockMode;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.ast.JoinType;
 import org.hibernate.sql.ast.spi.SqlAliasBase;
+import org.hibernate.sql.ast.tree.predicate.Predicate;
 
 /**
  * @author Steve Ebersole
@@ -23,7 +28,7 @@ public class StandardTableGroup extends AbstractTableGroup {
 
 	public StandardTableGroup(
 			NavigablePath navigablePath,
-			RootTableGroupProducer tableGroupProducer,
+			TableGroupProducer tableGroupProducer,
 			LockMode lockMode,
 			TableReference primaryTableReference,
 			List<TableReferenceJoin> tableJoins,
@@ -34,11 +39,6 @@ public class StandardTableGroup extends AbstractTableGroup {
 		this.tableJoins = tableJoins;
 	}
 
-	@Override
-	public RootTableGroupProducer getModelPart() {
-		return (RootTableGroupProducer) super.getModelPart();
-	}
-
 	@Override
 	public void applyAffectedTableNames(Consumer<String> nameCollector) {
 		// todo (6.0) : if we implement dynamic TableReference creation, this still needs to return the expressions for all mapped tables not just the ones with a TableReference at this time

hibernate-core/src/main/java/org/hibernate/sql/ast/tree/from/TableGroupBuilder.java

@@ -0,0 +1,131 @@
+/*
+ * 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.sql.ast.tree.from;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.function.Function;
+
+import org.hibernate.LockMode;
+import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBase;
+
+/**
+ * @author Steve Ebersole
+ */
+public class TableGroupBuilder implements TableReferenceCollector {
+	public static TableGroupBuilder builder(
+			NavigablePath path,
+			TableGroupProducer producer,
+			LockMode lockMode,
+			SqlAliasBase sqlAliasBase,
+			SessionFactoryImplementor sessionFactory) {
+		return new TableGroupBuilder( path, producer, lockMode, sqlAliasBase, sessionFactory );
+	}
+
+	private final NavigablePath path;
+	private final TableGroupProducer producer;
+	private final SessionFactoryImplementor sessionFactory;
+
+	private final SqlAliasBase sqlAliasBase;
+	private final LockMode lockMode;
+
+	private final Function<TableReference,TableReferenceJoin> primaryJoinProducer;
+
+	private TableReference primaryTableReference;
+	private TableReference secondaryTableLhs;
+
+	private java.util.List<TableReferenceJoin> tableJoins;
+
+	private TableGroupBuilder(
+			NavigablePath path,
+			TableGroupProducer producer,
+			LockMode lockMode,
+			SqlAliasBase sqlAliasBase,
+			SessionFactoryImplementor sessionFactory) {
+		this( path, producer, lockMode, sqlAliasBase, null, sessionFactory );
+	}
+
+	private TableGroupBuilder(
+			NavigablePath path,
+			TableGroupProducer producer,
+			LockMode lockMode,
+			SqlAliasBase sqlAliasBase,
+			Function<TableReference,TableReferenceJoin> primaryJoinProducer,
+			SessionFactoryImplementor sessionFactory) {
+		this.path = path;
+		this.producer = producer;
+		this.lockMode = lockMode;
+		this.sqlAliasBase = sqlAliasBase;
+		this.primaryJoinProducer = primaryJoinProducer;
+		this.sessionFactory = sessionFactory;
+	}
+
+	public TableGroup build() {
+		if ( primaryTableReference == null ) {
+			throw new IllegalStateException( "Primary TableReference was not specified : " + path );
+		}
+
+		return new StandardTableGroup(
+				path,
+				producer,
+				lockMode,
+				primaryTableReference,
+				tableJoins == null ? Collections.emptyList() : tableJoins,
+				sqlAliasBase,
+				sessionFactory
+		);
+	}
+
+	@Override
+	public void applyPrimaryReference(TableReference tableReference) {
+		if ( primaryTableReference != null ) {
+			assert primaryJoinProducer != null;
+
+			addTableReferenceJoin( primaryJoinProducer.apply( tableReference ) );
+
+		}
+		else {
+			primaryTableReference = tableReference;
+		}
+
+		secondaryTableLhs = tableReference;
+	}
+
+	@Override
+	public void applySecondaryTableReferences(
+			TableReference tableReference,
+			JoinType tableReferenceJoinType,
+			TableReferenceJoinPredicateProducer predicateProducer) {
+		if ( primaryTableReference == null ) {
+			primaryTableReference = tableReference;
+			secondaryTableLhs = primaryTableReference;
+		}
+		else {
+			addTableReferenceJoin(
+					new TableReferenceJoin(
+							tableReferenceJoinType,
+							tableReference,
+							predicateProducer.producePredicate(
+									secondaryTableLhs,
+									tableReference,
+									tableReferenceJoinType
+							)
+					)
+			);
+		}
+	}
+
+	public void addTableReferenceJoin(TableReferenceJoin join) {
+		if ( tableJoins == null ) {
+			tableJoins = new ArrayList<>();
+		}
+		tableJoins.add( join );
+	}
+}

hibernate-core/src/main/java/org/hibernate/sql/ast/tree/from/TableGroupProducer.java

@@ -15,7 +15,7 @@ import org.hibernate.query.sqm.sql.SqlAliasBaseManager;
  * @author Steve Ebersole
  * @author Andrea Boriero
  */
-public interface TableGroupProducer extends ModelPartContainer {
+public interface TableGroupProducer extends ModelPartContainer, TableReferenceContributor {
 	/**
 	 * Get the "stem" used as the base for generating SQL table aliases for table
 	 * references that are part of the TableGroup being generated

hibernate-core/src/main/java/org/hibernate/sql/ast/tree/from/TableReferenceCollector.java

@@ -0,0 +1,38 @@
+/*
+ * 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.sql.ast.tree.from;
+
+import org.hibernate.sql.ast.JoinType;
+
+/**
+ * Used in constructing {@link TableGroup} references to collect the individual table
+ * references
+ *
+ * @author Steve Ebersole
+ */
+public interface TableReferenceCollector {
+	void applyPrimaryReference(TableReference tableReference);
+
+	/**
+	 * Collect a table reference as part of the TableGroup.
+	 *
+	 * @param tableReference The TableReference.
+	 * @param joinType The type of join indicated by the mapping of the table, if it is to be joined
+	 * @param predicateProducer Function for creating the join predicate, if it is to be joined.  The first
+	 * 		argument passed to the function is the LHS reference.  The second is the same as `tableReference`.
+	 * 		The result is a SQL AST Predicate to use as the join-predicate
+	 */
+	void applySecondaryTableReferences(
+			TableReference tableReference,
+			JoinType joinType,
+			TableReferenceJoinPredicateProducer predicateProducer);
+
+	/**
+	 * Directly add a TableReferenceJoin
+	 */
+	void addTableReferenceJoin(TableReferenceJoin join);
+}

hibernate-core/src/main/java/org/hibernate/sql/ast/tree/from/TableReferenceContributor.java

@@ -6,19 +6,22 @@
  */
 package org.hibernate.sql.ast.tree.from;
 
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
 import org.hibernate.sql.ast.JoinType;
 import org.hibernate.sql.ast.spi.SqlAliasBase;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
 
 /**
  * @author Steve Ebersole
  */
 public interface TableReferenceContributor {
-//	/**
-//	 * Apply the Tables mapped by this producer to the collector as TableReferences
-//	 */
-//	void applyTableReferenceJoins(
-//			ColumnReferenceQualifier lhs,
-//			JoinType joinType,
-//			SqlAliasBase sqlAliasBase,
-//			TableReferenceJoinCollector joinCollector);
+	/**
+	 * Apply the Tables mapped by this producer to the collector as TableReferences
+	 */
+	void applyTableReferences(
+			SqlAliasBase sqlAliasBase,
+			JoinType baseJoinType,
+			TableReferenceCollector collector,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext);
 }

hibernate-core/src/main/java/org/hibernate/sql/ast/tree/from/TableReferenceJoinPredicateProducer.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.sql.ast.tree.from;
+
+import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.tree.predicate.Predicate;
+
+/**
+ * Functional contract for producing the join-predicate related to a {@link TableReferenceJoin}.
+ *
+ * @see TableReferenceJoin#getJoinPredicate
+ * @see TableReferenceCollector#applySecondaryTableReferences
+ *
+ * @author Steve Ebersole
+ */
+@FunctionalInterface
+public
+interface TableReferenceJoinPredicateProducer {
+	Predicate producePredicate(TableReference lhs, TableReference rhs, JoinType joinType);
+}

hibernate-core/src/main/java/org/hibernate/sql/results/internal/LoadingCollectionEntryImpl.java

@@ -0,0 +1,97 @@
+/*
+ * 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.sql.results.internal;
+
+import java.io.Serializable;
+
+import org.hibernate.collection.spi.PersistentCollection;
+import org.hibernate.engine.spi.CollectionEntry;
+import org.hibernate.engine.spi.PersistenceContext;
+import org.hibernate.engine.spi.SharedSessionContractImplementor;
+import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.sql.exec.spi.ExecutionContext;
+import org.hibernate.sql.results.spi.CollectionInitializer;
+import org.hibernate.sql.results.spi.LoadingCollectionEntry;
+
+/**
+ * Represents a collection currently being loaded.
+ *
+ * @author Steve Ebersole
+ */
+public class LoadingCollectionEntryImpl implements LoadingCollectionEntry {
+	private final CollectionPersister collectionDescriptor;
+	private final CollectionInitializer initializer;
+	private final Object key;
+	private final PersistentCollection collectionInstance;
+
+	public LoadingCollectionEntryImpl(
+			CollectionPersister collectionDescriptor,
+			CollectionInitializer initializer,
+			Object key,
+			PersistentCollection collectionInstance) {
+		this.collectionDescriptor = collectionDescriptor;
+		this.initializer = initializer;
+		this.key = key;
+		this.collectionInstance = collectionInstance;
+
+		collectionInstance.beforeInitialize( getCollectionDescriptor(), -1 );
+		collectionInstance.beginRead();
+	}
+
+	@Override public CollectionPersister getCollectionDescriptor() {
+		return collectionDescriptor;
+	}
+
+	/**
+	 * Access to the initializer that is responsible for initializing this collection
+	 */
+	@Override public CollectionInitializer getInitializer() {
+		return initializer;
+	}
+
+	@Override public Serializable getKey() {
+		// todo (6.0) : change from Serializable to Object
+		return (Serializable) key;
+	}
+
+	@Override public PersistentCollection getCollectionInstance() {
+		return collectionInstance;
+	}
+
+	@Override
+	public String toString() {
+		return getClass().getSimpleName() + "(" + getCollectionDescriptor().getNavigableRole().getFullPath() + "#" + getKey() + ")";
+	}
+
+	@Override public void finishLoading(ExecutionContext executionContext) {
+		collectionInstance.endRead();
+
+		final SharedSessionContractImplementor session = executionContext.getSession();
+		final PersistenceContext persistenceContext = session.getPersistenceContext();
+		final CollectionPersister collectionDescriptor = getCollectionDescriptor();
+
+		CollectionEntry collectionEntry = persistenceContext.getCollectionEntry( collectionInstance );
+		if ( collectionEntry == null ) {
+			collectionEntry = persistenceContext.addInitializedCollection(
+					collectionDescriptor,
+					getCollectionInstance(),
+					getKey()
+			);
+		}
+		else {
+			collectionEntry.postInitialize( collectionInstance );
+		}
+
+		if ( collectionDescriptor.getCollectionType().hasHolder() ) {
+			persistenceContext.addCollectionHolder( collectionInstance );
+		}
+
+
+		// todo (6.0) : there is other logic still needing to be implemented here.  caching, etc
+		// 		see org.hibernate.engine.loading.internal.CollectionLoadContext#endLoadingCollection in 5.x
+	}
+}

hibernate-core/src/main/java/org/hibernate/sql/results/internal/StandardRowReader.java

@@ -11,7 +11,9 @@ import java.util.List;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.query.named.RowReaderMemento;
 import org.hibernate.sql.exec.spi.Callback;
+import org.hibernate.sql.results.spi.CollectionInitializer;
 import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.EntityInitializer;
 import org.hibernate.sql.results.spi.Initializer;
 import org.hibernate.sql.results.spi.JdbcValuesSourceProcessingOptions;
 import org.hibernate.sql.results.spi.JdbcValuesSourceProcessingState;
@@ -125,7 +127,17 @@ public class StandardRowReader<T> implements RowReader<T> {
 		// old
 
 		for ( int i = 0; i < initializers.size(); i++ ) {
-			initializers.get( i ).resolveKey( rowProcessingState );
+			final Initializer initializer = initializers.get( i );
+			if ( ! ( initializer instanceof CollectionInitializer ) ) {
+				initializer.resolveKey( rowProcessingState );
+			}
+		}
+
+		for ( int i = 0; i < initializers.size(); i++ ) {
+			final Initializer initializer = initializers.get( i );
+			if ( initializer instanceof CollectionInitializer ) {
+				initializer.resolveKey( rowProcessingState );
+			}
 		}
 
 		for ( int i = 0; i < initializers.size(); i++ ) {

hibernate-core/src/main/java/org/hibernate/sql/results/internal/domain/collection/CollectionFetch.java

@@ -0,0 +1,56 @@
+/*
+ * 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.sql.results.internal.domain.collection;
+
+import org.hibernate.metamodel.mapping.PluralAttributeMapping;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.results.spi.Fetch;
+import org.hibernate.sql.results.spi.FetchParent;
+
+/**
+ * @author Steve Ebersole
+ */
+public abstract class CollectionFetch implements Fetch {
+	private final NavigablePath fetchedPath;
+	private final PluralAttributeMapping fetchedAttribute;
+
+	private final boolean nullable;
+
+	private final FetchParent fetchParent;
+
+	public CollectionFetch(
+			NavigablePath fetchedPath,
+			PluralAttributeMapping fetchedAttribute,
+			boolean nullable,
+			FetchParent fetchParent) {
+		this.fetchedPath = fetchedPath;
+		this.fetchedAttribute = fetchedAttribute;
+		this.fetchParent = fetchParent;
+		this.nullable = nullable;
+	}
+
+	@Override
+	public FetchParent getFetchParent() {
+		return fetchParent;
+	}
+
+	@Override
+	public PluralAttributeMapping getFetchedMapping() {
+		return fetchedAttribute;
+	}
+
+	@Override
+	public NavigablePath getNavigablePath() {
+		return fetchedPath;
+	}
+
+	@Override
+	public boolean isNullable() {
+		return nullable;
+	}
+}

hibernate-core/src/main/java/org/hibernate/sql/results/internal/domain/collection/DelayedCollectionAssembler.java

@@ -0,0 +1,155 @@
+/*
+ * 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.sql.results.internal.domain.collection;
+
+import java.io.Serializable;
+import java.util.function.Consumer;
+
+import org.hibernate.collection.spi.CollectionSemantics;
+import org.hibernate.collection.spi.PersistentCollection;
+import org.hibernate.engine.spi.CollectionKey;
+import org.hibernate.engine.spi.PersistenceContext;
+import org.hibernate.engine.spi.SharedSessionContractImplementor;
+import org.hibernate.metamodel.mapping.PluralAttributeMapping;
+import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.results.spi.AssemblerCreationState;
+import org.hibernate.sql.results.spi.CollectionInitializer;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.FetchParentAccess;
+import org.hibernate.sql.results.spi.Initializer;
+import org.hibernate.sql.results.spi.JdbcValuesSourceProcessingOptions;
+import org.hibernate.sql.results.spi.LoadingCollectionEntry;
+import org.hibernate.sql.results.spi.RowProcessingState;
+import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
+
+/**
+ * @author Steve Ebersole
+ */
+public class DelayedCollectionAssembler implements DomainResultAssembler {
+	private final PluralAttributeMapping fetchedMapping;
+	private final FetchParentAccess parentAccess;
+
+	private final CollectionInitializer initializer;
+
+	public DelayedCollectionAssembler(
+			NavigablePath fetchPath,
+			PluralAttributeMapping fetchedMapping,
+			FetchParentAccess parentAccess,
+			Consumer<Initializer> collector,
+			AssemblerCreationState creationState) {
+		this.fetchedMapping = fetchedMapping;
+		this.parentAccess = parentAccess;
+		this.initializer = new InitializerImpl( fetchPath, fetchedMapping, parentAccess, creationState );
+		collector.accept( initializer );
+	}
+
+	@Override
+	public Object assemble(RowProcessingState rowProcessingState, JdbcValuesSourceProcessingOptions options) {
+		return initializer.getCollectionInstance();
+	}
+
+	@Override
+	public JavaTypeDescriptor getAssembledJavaTypeDescriptor() {
+		return fetchedMapping.getJavaTypeDescriptor();
+	}
+
+	private static class InitializerImpl implements CollectionInitializer {
+		private final NavigablePath fetchedPath;
+		private final PluralAttributeMapping fetchedMapping;
+		private final FetchParentAccess parentAccess;
+
+		private CollectionKey collectionKey;
+		private PersistentCollection instance;
+
+		public InitializerImpl(
+				NavigablePath fetchedPath,
+				PluralAttributeMapping fetchedMapping,
+				FetchParentAccess parentAccess,
+				AssemblerCreationState creationState) {
+			this.fetchedPath = fetchedPath;
+			this.fetchedMapping = fetchedMapping;
+			this.parentAccess = parentAccess;
+		}
+
+		@Override
+		public NavigablePath getNavigablePath() {
+			return fetchedPath;
+		}
+
+		@Override
+		public void resolveKey(RowProcessingState rowProcessingState) {
+			if ( collectionKey != null ) {
+				// already resolved
+				return;
+			}
+
+			collectionKey = new CollectionKey(
+					fetchedMapping.getCollectionDescriptor(),
+					parentAccess.getParentKey()
+			);
+		}
+
+		@Override
+		public void resolveInstance(RowProcessingState rowProcessingState) {
+			final SharedSessionContractImplementor session = rowProcessingState.getSession();
+			final PersistenceContext persistenceContext = session.getPersistenceContext();
+			final LoadingCollectionEntry loadingEntry = persistenceContext.getLoadContexts().findLoadingCollectionEntry( collectionKey );
+			final PersistentCollection registeredInstance = persistenceContext.getCollection( collectionKey );
+
+			if ( loadingEntry != null ) {
+				instance = loadingEntry.getCollectionInstance();
+				return;
+			}
+
+			if ( registeredInstance != null ) {
+				this.instance = registeredInstance;
+				return;
+			}
+
+			this.instance = makePersistentCollection( fetchedMapping, collectionKey, rowProcessingState );
+			persistenceContext.addUninitializedCollection(
+					getInitializingCollectionDescriptor(),
+					instance,
+					(Serializable) collectionKey.getKey()
+			);
+		}
+
+		private static PersistentCollection makePersistentCollection(
+				PluralAttributeMapping fetchedMapping,
+				CollectionKey collectionKey,
+				RowProcessingState rowProcessingState) {
+			final CollectionPersister collectionDescriptor = fetchedMapping.getCollectionDescriptor();
+			final CollectionSemantics collectionSemantics = collectionDescriptor.getCollectionSemantics();
+			return collectionSemantics.instantiateWrapper(
+					collectionKey.getKey(),
+					collectionDescriptor,
+					rowProcessingState.getSession()
+			);
+		}
+
+		@Override
+		public void initializeInstance(RowProcessingState rowProcessingState) {
+		}
+
+		@Override
+		public void finishUpRow(RowProcessingState rowProcessingState) {
+			collectionKey = null;
+			instance = null;
+		}
+
+		@Override
+		public CollectionPersister getInitializingCollectionDescriptor() {
+			return fetchedMapping.getCollectionDescriptor();
+		}
+
+		@Override
+		public PersistentCollection getCollectionInstance() {
+			return instance;
+		}
+	}
+}

hibernate-core/src/main/java/org/hibernate/sql/results/internal/domain/collection/DelayedCollectionFetch.java

@@ -0,0 +1,44 @@
+/*
+ * 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.sql.results.internal.domain.collection;
+
+import java.util.function.Consumer;
+
+import org.hibernate.metamodel.mapping.PluralAttributeMapping;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.results.spi.AssemblerCreationState;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.FetchParent;
+import org.hibernate.sql.results.spi.FetchParentAccess;
+import org.hibernate.sql.results.spi.Initializer;
+
+/**
+ * @author Steve Ebersole
+ */
+public class DelayedCollectionFetch extends CollectionFetch {
+	public DelayedCollectionFetch(
+			NavigablePath fetchedPath,
+			PluralAttributeMapping fetchedAttribute,
+			boolean nullable,
+			FetchParent fetchParent) {
+		super( fetchedPath, fetchedAttribute, nullable, fetchParent );
+	}
+
+	@Override
+	public DomainResultAssembler createAssembler(
+			FetchParentAccess parentAccess,
+			Consumer<Initializer> collector,
+			AssemblerCreationState creationState) {
+		return new DelayedCollectionAssembler(
+				getNavigablePath(),
+				getFetchedMapping(),
+				parentAccess,
+				collector,
+				creationState
+		);
+	}
+}

hibernate-core/src/main/java/org/hibernate/sql/results/internal/domain/collection/EagerCollectionAssembler.java

@@ -0,0 +1,258 @@
+/*
+ * 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.sql.results.internal.domain.collection;
+
+import java.util.function.Consumer;
+
+import org.hibernate.collection.spi.CollectionSemantics;
+import org.hibernate.collection.spi.PersistentCollection;
+import org.hibernate.engine.spi.CollectionKey;
+import org.hibernate.engine.spi.PersistenceContext;
+import org.hibernate.metamodel.mapping.PluralAttributeMapping;
+import org.hibernate.persister.collection.CollectionPersister;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.results.internal.LoadingCollectionEntryImpl;
+import org.hibernate.sql.results.spi.AssemblerCreationState;
+import org.hibernate.sql.results.spi.CollectionInitializer;
+import org.hibernate.sql.results.spi.DomainResult;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.Fetch;
+import org.hibernate.sql.results.spi.FetchParentAccess;
+import org.hibernate.sql.results.spi.Initializer;
+import org.hibernate.sql.results.spi.JdbcValuesSourceProcessingOptions;
+import org.hibernate.sql.results.spi.LoadContexts;
+import org.hibernate.sql.results.spi.LoadingCollectionEntry;
+import org.hibernate.sql.results.spi.RowProcessingState;
+import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
+
+/**
+ * @author Steve Ebersole
+ */
+public class EagerCollectionAssembler implements DomainResultAssembler {
+	private final PluralAttributeMapping fetchedMapping;
+	private final FetchParentAccess parentAccess;
+
+	private final CollectionInitializer initializer;
+
+	public EagerCollectionAssembler(
+			NavigablePath fetchPath,
+			PluralAttributeMapping fetchedMapping,
+			DomainResult fkResult,
+			Fetch elementFetch,
+			Fetch indexFetch,
+			DomainResult identifierResult,
+			FetchParentAccess parentAccess,
+			Consumer<Initializer> collector,
+			AssemblerCreationState creationState) {
+		this.fetchedMapping = fetchedMapping;
+		this.parentAccess = parentAccess;
+
+		this.initializer = new InitializerImpl(
+				fetchPath,
+				fetchedMapping,
+				parentAccess,
+				fkResult,
+				elementFetch,
+				indexFetch,
+				identifierResult,
+				collector,
+				creationState
+		);
+
+		collector.accept( initializer );
+	}
+
+	@Override
+	public Object assemble(RowProcessingState rowProcessingState, JdbcValuesSourceProcessingOptions options) {
+		return initializer.getCollectionInstance();
+	}
+
+	@Override
+	public JavaTypeDescriptor getAssembledJavaTypeDescriptor() {
+		return fetchedMapping.getJavaTypeDescriptor();
+	}
+
+	private static class InitializerImpl implements CollectionInitializer {
+		private final NavigablePath fetchedPath;
+		private final PluralAttributeMapping fetchedMapping;
+		private final FetchParentAccess parentAccess;
+
+		private final DomainResultAssembler fkAssembler;
+		private final DomainResultAssembler elementAssembler;
+		private final DomainResultAssembler indexAssembler;
+		private final DomainResultAssembler identifierAssembler;
+
+		private CollectionKey collectionKey;
+
+		private boolean managing;
+		private Object fkValue;
+
+		// todo (6.0) : consider using the initializer itself as the holder of the various "temp" collections
+		//  		used while reading a collection.  that would mean collection-type specific initializers (List, versus Set)
+		private PersistentCollection instance;
+
+		public InitializerImpl(
+				NavigablePath fetchedPath,
+				PluralAttributeMapping fetchedMapping,
+				FetchParentAccess parentAccess,
+				DomainResult fkResult,
+				Fetch elementFetch,
+				Fetch indexFetch,
+				DomainResult identifierResult,
+				Consumer<Initializer> collector,
+				AssemblerCreationState creationState) {
+			this.fetchedPath = fetchedPath;
+			this.fetchedMapping = fetchedMapping;
+			this.parentAccess = parentAccess;
+
+			this.fkAssembler = fkResult.createResultAssembler( collector, creationState );
+
+			// questionable what should be the parent access here
+			this.elementAssembler = elementFetch.createAssembler( parentAccess, collector, creationState );
+			this.indexAssembler = indexFetch == null
+					? null
+					: indexFetch.createAssembler( parentAccess, collector, creationState );
+			this.identifierAssembler = identifierResult == null
+					? null
+					: identifierResult.createResultAssembler( collector, creationState );
+		}
+
+		@Override
+		public CollectionPersister getInitializingCollectionDescriptor() {
+			return fetchedMapping.getCollectionDescriptor();
+		}
+
+		@Override
+		public PersistentCollection getCollectionInstance() {
+			return instance;
+		}
+
+		@Override
+		public NavigablePath getNavigablePath() {
+			return fetchedPath;
+		}
+
+		@Override
+		public void finishUpRow(RowProcessingState rowProcessingState) {
+			collectionKey = null;
+			managing = false;
+			instance = null;
+		}
+
+		@Override
+		public void resolveKey(RowProcessingState rowProcessingState) {
+			if ( collectionKey != null ) {
+				// already resolved
+				return;
+			}
+
+			collectionKey = new CollectionKey(
+					fetchedMapping.getCollectionDescriptor(),
+					parentAccess.getParentKey()
+			);
+
+			final Object fkValue = fkAssembler.assemble( rowProcessingState );
+			if ( fkValue == null ) {
+				// this row has no collection element
+				return;
+			}
+		}
+
+		@Override
+		public void resolveInstance(RowProcessingState rowProcessingState) {
+			if ( instance != null ) {
+				// already resolved
+				return;
+			}
+
+			final PersistenceContext persistenceContext = rowProcessingState.getSession().getPersistenceContext();
+
+			// see if the collection is already being initialized
+
+			final LoadContexts loadContexts = persistenceContext.getLoadContexts();
+			final LoadingCollectionEntry existingEntry = loadContexts.findLoadingCollectionEntry( collectionKey );
+
+			if ( existingEntry != null ) {
+				this.instance = existingEntry.getCollectionInstance();
+				if ( existingEntry.getInitializer() == this ) {
+					this.managing = true;
+				}
+				return;
+			}
+
+			// see if it has been already registered with the Session
+
+			final PersistentCollection registeredInstance = persistenceContext.getCollection( collectionKey );
+			if ( registeredInstance != null ) {
+				this.instance = registeredInstance;
+				// it was already registered, so use that wrapper.
+				if ( ! registeredInstance.wasInitialized() ) {
+					// if the existing wrapper is not initialized, we will take responsibility for initializing it
+					managing = true;
+					rowProcessingState.getJdbcValuesSourceProcessingState().registerLoadingCollection(
+							collectionKey,
+							new LoadingCollectionEntryImpl(
+									getInitializingCollectionDescriptor(),
+									this,
+									collectionKey,
+									registeredInstance
+							)
+					);
+					return;
+				}
+			}
+
+			this.instance = makePersistentCollection( fetchedMapping, collectionKey, rowProcessingState );
+			this.managing = true;
+
+			rowProcessingState.getJdbcValuesSourceProcessingState().registerLoadingCollection(
+					collectionKey,
+					new LoadingCollectionEntryImpl(
+							fetchedMapping.getCollectionDescriptor(),
+							this,
+							collectionKey.getKey(),
+							instance
+					)
+			);
+
+		}
+
+		private static PersistentCollection makePersistentCollection(
+				PluralAttributeMapping fetchedMapping,
+				CollectionKey collectionKey,
+				RowProcessingState rowProcessingState) {
+			final CollectionPersister collectionDescriptor = fetchedMapping.getCollectionDescriptor();
+			final CollectionSemantics collectionSemantics = collectionDescriptor.getCollectionSemantics();
+			return collectionSemantics.instantiateWrapper(
+					collectionKey.getKey(),
+					collectionDescriptor,
+					rowProcessingState.getSession()
+			);
+		}
+
+		@Override
+		public void initializeInstance(RowProcessingState rowProcessingState) {
+			if ( ! managing ) {
+				return;
+			}
+
+			final Object fkValue = fkAssembler.assemble( rowProcessingState );
+			if ( fkValue == null ) {
+				// this row contains no collection element
+				return;
+			}
+
+			getCollectionInstance().readFrom(
+					rowProcessingState,
+					elementAssembler,
+					indexAssembler,
+					identifierAssembler,
+					parentAccess.getFetchParentInstance()
+			);
+		}
+	}
+}

hibernate-core/src/main/java/org/hibernate/sql/results/internal/domain/collection/EagerCollectionFetch.java

@@ -0,0 +1,125 @@
+/*
+ * 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.sql.results.internal.domain.collection;
+
+import java.util.List;
+import java.util.function.Consumer;
+
+import org.hibernate.metamodel.mapping.CollectionIdentifierDescriptor;
+import org.hibernate.metamodel.mapping.CollectionPart;
+import org.hibernate.metamodel.mapping.PluralAttributeMapping;
+import org.hibernate.query.NavigablePath;
+import org.hibernate.sql.ast.tree.from.TableGroup;
+import org.hibernate.sql.results.spi.AssemblerCreationState;
+import org.hibernate.sql.results.spi.DomainResult;
+import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.sql.results.spi.DomainResultCreationState;
+import org.hibernate.sql.results.spi.Fetch;
+import org.hibernate.sql.results.spi.FetchParent;
+import org.hibernate.sql.results.spi.FetchParentAccess;
+import org.hibernate.sql.results.spi.FetchableContainer;
+import org.hibernate.sql.results.spi.Initializer;
+import org.hibernate.type.descriptor.java.JavaTypeDescriptor;
+
+/**
+ * @author Steve Ebersole
+ */
+public class EagerCollectionFetch extends CollectionFetch implements FetchParent {
+	private final DomainResult fkResult;
+
+	private final Fetch elementFetch;
+	private final Fetch indexFetch;
+	private final DomainResult identifierResult;
+
+	private final List<Fetch> fetches;
+
+	public EagerCollectionFetch(
+			NavigablePath fetchedPath,
+			PluralAttributeMapping fetchedAttribute,
+			DomainResult fkResult,
+			boolean nullable,
+			FetchParent fetchParent,
+			DomainResultCreationState creationState) {
+		super( fetchedPath, fetchedAttribute, nullable, fetchParent );
+		this.fkResult = fkResult;
+
+		final CollectionIdentifierDescriptor identifierDescriptor = fetchedAttribute.getIdentifierDescriptor();
+		if ( identifierDescriptor == null ) {
+			this.identifierResult = null;
+		}
+		else {
+			final TableGroup collectionTableGroup = creationState.getSqlAstCreationState().getFromClauseAccess().getTableGroup( fetchedPath );
+			this.identifierResult = identifierDescriptor.createDomainResult( fetchedPath, collectionTableGroup, creationState );
+		}
+
+		fetches = creationState.visitFetches( this );
+		if ( fetchedAttribute.getIndexDescriptor() != null ) {
+			assert fetches.size() == 2;
+			indexFetch = fetches.get( 0 );
+			elementFetch = fetches.get( 1 );
+		}
+		else {
+			assert fetches.size() == 1;
+			indexFetch = null;
+			elementFetch = fetches.get( 0 );
+		}
+	}
+
+	@Override
+	public DomainResultAssembler createAssembler(
+			FetchParentAccess parentAccess,
+			Consumer<Initializer> collector,
+			AssemblerCreationState creationState) {
+		return new EagerCollectionAssembler(
+				getNavigablePath(),
+				getFetchedMapping(),
+				fkResult,
+				elementFetch,
+				indexFetch,
+				identifierResult,
+				parentAccess,
+				collector,
+				creationState
+		);
+	}
+
+	@Override
+	public FetchableContainer getReferencedMappingContainer() {
+		return getFetchedMapping();
+	}
+
+	@Override
+	public PluralAttributeMapping getReferencedMappingType() {
+		return getFetchedMapping();
+	}
+
+	@Override
+	public List<Fetch> getFetches() {
+		return fetches;
+	}
+
+	@Override
+	public Fetch findFetch(String fetchableName) {
+		if ( CollectionPart.Nature.ELEMENT.getName().equals( fetchableName ) ) {
+			return elementFetch;
+		}
+		else if ( CollectionPart.Nature.INDEX.getName().equals( fetchableName ) ) {
+			return indexFetch;
+		}
+		else {
+			throw new IllegalArgumentException(
+					"Unknown fetchable [" + getFetchedMapping().getCollectionDescriptor().getRole() +
+							" -> " + fetchableName + "]"
+			);
+		}
+	}
+
+	@Override
+	public JavaTypeDescriptor getResultJavaTypeDescriptor() {
+		return getFetchedMapping().getJavaTypeDescriptor();
+	}
+}

hibernate-core/src/main/java/org/hibernate/sql/results/internal/domain/composite/CompositeFetch.java

@@ -10,7 +10,7 @@ import java.util.function.Consumer;
 
 import org.hibernate.engine.FetchTiming;
 import org.hibernate.metamodel.mapping.EmbeddableMappingType;
-import org.hibernate.metamodel.mapping.internal.EmbeddedAttributeMapping;
+import org.hibernate.metamodel.mapping.EmbeddableValuedModelPart;
 import org.hibernate.query.NavigablePath;
 import org.hibernate.sql.results.internal.domain.AbstractFetchParent;
 import org.hibernate.sql.results.spi.AssemblerCreationState;
@@ -29,17 +29,20 @@ import org.hibernate.sql.results.spi.Initializer;
 public class CompositeFetch extends AbstractFetchParent implements CompositeResultMappingNode, Fetch {
 	private final FetchParent fetchParent;
 	private final FetchTiming fetchTiming;
+	private final boolean nullable;
 
 	public CompositeFetch(
 			NavigablePath navigablePath,
-			EmbeddedAttributeMapping embeddedAttribute,
+			EmbeddableValuedModelPart embeddedPartDescriptor,
 			FetchParent fetchParent,
 			FetchTiming fetchTiming,
+			boolean nullable,
 			DomainResultCreationState creationState) {
-		super( embeddedAttribute, navigablePath );
+		super( embeddedPartDescriptor, navigablePath );
 
 		this.fetchParent = fetchParent;
 		this.fetchTiming = fetchTiming;
+		this.nullable = nullable;
 
 		creationState.getSqlAstCreationState().getFromClauseAccess().registerTableGroup(
 				getNavigablePath(),
@@ -49,38 +52,34 @@ public class CompositeFetch extends AbstractFetchParent implements CompositeResu
 		afterInitialize( creationState );
 	}
 
-	public EmbeddedAttributeMapping getEmbeddedAttributeMapping() {
-		return (EmbeddedAttributeMapping) super.getFetchContainer();
-	}
-
 	@Override
 	public FetchParent getFetchParent() {
 		return fetchParent;
 	}
 
 	@Override
-	public EmbeddedAttributeMapping getFetchContainer() {
-		return getEmbeddedAttributeMapping();
+	public EmbeddableValuedModelPart getFetchContainer() {
+		return (EmbeddableValuedModelPart) super.getFetchContainer();
 	}
 
 	@Override
-	public EmbeddedAttributeMapping getReferencedMappingContainer() {
-		return getEmbeddedAttributeMapping();
+	public EmbeddableValuedModelPart getReferencedMappingContainer() {
+		return getFetchContainer();
 	}
 
 	@Override
 	public Fetchable getFetchedMapping() {
-		return getEmbeddedAttributeMapping();
+		return getFetchContainer();
 	}
 
 	@Override
 	public EmbeddableMappingType getReferencedMappingType() {
-		return getEmbeddedAttributeMapping().getEmbeddableTypeDescriptor();
+		return getFetchContainer().getEmbeddableTypeDescriptor();
 	}
 
 	@Override
 	public boolean isNullable() {
-		return getEmbeddedAttributeMapping().getAttributeMetadataAccess().resolveAttributeMetadata( null ).isNullable();
+		return nullable;
 	}
 
 	@Override

hibernate-core/src/main/java/org/hibernate/sql/results/internal/domain/composite/CompositeFetchInitializer.java

@@ -27,4 +27,9 @@ public class CompositeFetchInitializer
 			AssemblerCreationState creationState) {
 		super( resultDescriptor, fetchParentAccess, initializerConsumer, creationState );
 	}
+
+	@Override
+	public Object getParentKey() {
+		return getFetchParentAccess().getParentKey();
+	}
 }

hibernate-core/src/main/java/org/hibernate/sql/results/internal/domain/composite/CompositeRootInitializer.java

@@ -22,4 +22,9 @@ public class CompositeRootInitializer extends AbstractCompositeInitializer {
 			AssemblerCreationState creationState) {
 		super( resultDescriptor, null, initializerConsumer, creationState );
 	}
+
+	@Override
+	public Object getParentKey() {
+		return null;
+	}
 }

hibernate-core/src/main/java/org/hibernate/sql/results/internal/domain/entity/AbstractEntityInitializer.java

@@ -34,7 +34,6 @@ import org.hibernate.event.spi.PreLoadEvent;
 import org.hibernate.event.spi.PreLoadEventListener;
 import org.hibernate.internal.util.StringHelper;
 import org.hibernate.metamodel.mapping.AttributeMapping;
-import org.hibernate.metamodel.mapping.StateArrayContributorMapping;
 import org.hibernate.persister.entity.EntityPersister;
 import org.hibernate.persister.entity.Loadable;
 import org.hibernate.proxy.HibernateProxy;
@@ -197,6 +196,11 @@ public abstract class AbstractEntityInitializer extends AbstractFetchParentAcces
 		return entityKey.getIdentifier();
 	}
 
+	@Override
+	public Object getParentKey() {
+		return getKeyValue();
+	}
+
 	@Override
 	public Object getFetchParentInstance() {
 		if ( entityInstance == null ) {

hibernate-core/src/main/java/org/hibernate/sql/results/internal/domain/entity/EntityResultImpl.java

@@ -25,8 +25,6 @@ import org.hibernate.sql.results.spi.EntityResult;
 public class EntityResultImpl extends AbstractEntityResultNode implements EntityResult {
 	private final String resultVariable;
 
-
-
 	public EntityResultImpl(
 			NavigablePath navigablePath,
 			EntityValuedModelPart entityValuedModelPart,

hibernate-core/src/main/java/org/hibernate/sql/results/spi/FetchParent.java

@@ -8,7 +8,7 @@ package org.hibernate.sql.results.spi;
 
 import java.util.List;
 
-import org.hibernate.metamodel.mapping.ManagedMappingType;
+import org.hibernate.metamodel.mapping.MappingType;
 import org.hibernate.query.NavigablePath;
 
 /**
@@ -22,7 +22,7 @@ public interface FetchParent extends ResultSetMappingNode {
 	/**
 	 * This parent's type
 	 */
-	ManagedMappingType getReferencedMappingType();
+	FetchableContainer getReferencedMappingType();
 
 	/**
 	 * Get the property path to this parent

hibernate-core/src/main/java/org/hibernate/sql/results/spi/FetchParentAccess.java

@@ -19,6 +19,8 @@ import org.hibernate.query.NavigablePath;
 public interface FetchParentAccess {
 	FetchParentAccess findFirstEntityDescriptorAccess();
 
+	Object getParentKey();
+
 	/**
 	 * Access to the fetch's parent instance.
 	 */

hibernate-core/src/main/java/org/hibernate/sql/results/spi/FetchableContainer.java

@@ -15,6 +15,8 @@ import org.hibernate.metamodel.mapping.ModelPartContainer;
  * @author Steve Ebersole
  */
 public interface FetchableContainer extends ModelPartContainer {
+	int getNumberOfFetchables();
+
 	default void visitKeyFetchables(
 			Consumer<Fetchable> fetchableConsumer,
 			EntityMappingType treatTargetType) {

hibernate-core/src/main/java/org/hibernate/sql/results/spi/LoadContexts.java

@@ -6,8 +6,6 @@
  */
 package org.hibernate.sql.results.spi;
 
-import java.sql.ResultSet;
-
 import org.hibernate.engine.spi.CollectionKey;
 import org.hibernate.engine.spi.EntityKey;
 import org.hibernate.engine.spi.PersistenceContext;
@@ -18,7 +16,7 @@ import org.hibernate.internal.util.collections.StandardStack;
 
 /**
  * Maintains a Stack of processing state related to performing load operations.
- * The sCollectionLoadContexttate is defined by {@link JdbcValuesSourceProcessingState} which
+ * The state is defined by {@link JdbcValuesSourceProcessingState} which
  * encapsulates the data to be processed by the load whether the data comes from
  * a ResultSet or second-level cache hit.
  *

hibernate-core/src/main/java/org/hibernate/sql/results/spi/LoadingCollectionEntry.java

@@ -9,9 +9,6 @@ package org.hibernate.sql.results.spi;
 import java.io.Serializable;
 
 import org.hibernate.collection.spi.PersistentCollection;
-import org.hibernate.engine.spi.CollectionEntry;
-import org.hibernate.engine.spi.PersistenceContext;
-import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.persister.collection.CollectionPersister;
 import org.hibernate.sql.exec.spi.ExecutionContext;
 
@@ -20,76 +17,14 @@ import org.hibernate.sql.exec.spi.ExecutionContext;
  *
  * @author Steve Ebersole
  */
-public class LoadingCollectionEntry {
-	private final CollectionPersister collectionDescriptor;
-	private final CollectionInitializer initializer;
-	// todo (6.0) : change from Serializable to Object
-	private final Serializable key;
-	private final PersistentCollection collectionInstance;
+public interface LoadingCollectionEntry {
+	CollectionPersister getCollectionDescriptor();
 
-	public LoadingCollectionEntry(
-			CollectionPersister collectionDescriptor,
-			CollectionInitializer initializer,
-			Serializable key,
-			PersistentCollection collectionInstance) {
-		this.collectionDescriptor = collectionDescriptor;
-		this.initializer = initializer;
-		this.key = key;
-		this.collectionInstance = collectionInstance;
+	CollectionInitializer getInitializer();
 
-		collectionInstance.beforeInitialize( getCollectionDescriptor(), -1 );
-		collectionInstance.beginRead();
-	}
+	Serializable getKey();
 
-	public CollectionPersister getCollectionDescriptor() {
-		return collectionDescriptor;
-	}
+	PersistentCollection getCollectionInstance();
 
-	/**
-	 * Access to the initializer that is responsible for initializing this collection
-	 */
-	public CollectionInitializer getInitializer() {
-		return initializer;
-	}
-
-	public Serializable getKey() {
-		return key;
-	}
-
-	public PersistentCollection getCollectionInstance() {
-		return collectionInstance;
-	}
-
-	@Override
-	public String toString() {
-		return getClass().getSimpleName() + "(" + getCollectionDescriptor().getNavigableRole().getFullPath() + "#" + getKey() + ")";
-	}
-
-	public void finishLoading(ExecutionContext executionContext) {
-		collectionInstance.endRead();
-
-		final SharedSessionContractImplementor session = executionContext.getSession();
-		final PersistenceContext persistenceContext = session.getPersistenceContext();
-		final CollectionPersister collectionDescriptor = getCollectionDescriptor();
-
-		CollectionEntry collectionEntry = persistenceContext.getCollectionEntry( collectionInstance );
-		if ( collectionEntry == null ) {
-			collectionEntry = persistenceContext.addInitializedCollection(
-					collectionDescriptor,
-					getCollectionInstance(),
-					getKey()
-			);
-		}
-		else {
-			collectionEntry.postInitialize( collectionInstance );
-		}
-
-		if ( collectionDescriptor.getCollectionType().hasHolder() ) {
-			persistenceContext.addCollectionHolder( collectionInstance );
-		}
-
-
-		// todo (6.0) : there is other logic still needing to be implemented here.  caching, etc
-		// 		see org.hibernate.engine.loading.internal.CollectionLoadContext#endLoadingCollection in 5.x
-	}
+	void finishLoading(ExecutionContext executionContext);
 }

hibernate-core/src/main/java/org/hibernate/type/descriptor/java/BooleanTypeDescriptor.java

@@ -7,6 +7,7 @@
 package org.hibernate.type.descriptor.java;
 
 import org.hibernate.type.descriptor.WrapperOptions;
+import org.hibernate.type.descriptor.java.spi.Primitive;
 
 import static java.lang.Boolean.FALSE;
 import static java.lang.Boolean.TRUE;
@@ -16,7 +17,7 @@ import static java.lang.Boolean.TRUE;
  *
  * @author Steve Ebersole
  */
-public class BooleanTypeDescriptor extends AbstractTypeDescriptor<Boolean> {
+public class BooleanTypeDescriptor extends AbstractTypeDescriptor<Boolean> implements Primitive<Boolean> {
 	public static final BooleanTypeDescriptor INSTANCE = new BooleanTypeDescriptor();
 
 	private final char characterValueTrue;
@@ -130,4 +131,14 @@ public class BooleanTypeDescriptor extends AbstractTypeDescriptor<Boolean> {
 	public Long toLong(Boolean value) {
 		return (long) toInt( value );
 	}
+
+	@Override
+	public Class getPrimitiveClass() {
+		return boolean.class;
+	}
+
+	@Override
+	public Boolean getDefaultValue() {
+		return FALSE;
+	}
 }

hibernate-core/src/main/java/org/hibernate/type/descriptor/java/ByteTypeDescriptor.java

@@ -6,6 +6,7 @@
  */
 package org.hibernate.type.descriptor.java;
 import org.hibernate.type.descriptor.WrapperOptions;
+import org.hibernate.type.descriptor.java.spi.Primitive;
 
 /**
  * Descriptor for {@link Byte} handling.
@@ -13,7 +14,7 @@ import org.hibernate.type.descriptor.WrapperOptions;
  * @author Steve Ebersole
  * @author Lukasz Antoniak (lukasz dot antoniak at gmail dot com)
  */
-public class ByteTypeDescriptor extends AbstractTypeDescriptor<Byte> {
+public class ByteTypeDescriptor extends AbstractTypeDescriptor<Byte> implements Primitive<Byte> {
 	public static final ByteTypeDescriptor INSTANCE = new ByteTypeDescriptor();
 
 	public ByteTypeDescriptor() {
@@ -58,6 +59,7 @@ public class ByteTypeDescriptor extends AbstractTypeDescriptor<Byte> {
 		}
 		throw unknownUnwrap( type );
 	}
+
 	@Override
 	public <X> Byte wrap(X value, WrapperOptions options) {
 		if ( value == null ) {
@@ -74,4 +76,14 @@ public class ByteTypeDescriptor extends AbstractTypeDescriptor<Byte> {
 		}
 		throw unknownWrap( value.getClass() );
 	}
+
+	@Override
+	public Class getPrimitiveClass() {
+		return byte.class;
+	}
+
+	@Override
+	public Byte getDefaultValue() {
+		return 0;
+	}
 }

hibernate-core/src/main/java/org/hibernate/type/descriptor/java/CharacterTypeDescriptor.java

@@ -7,13 +7,14 @@
 package org.hibernate.type.descriptor.java;
 import org.hibernate.HibernateException;
 import org.hibernate.type.descriptor.WrapperOptions;
+import org.hibernate.type.descriptor.java.spi.Primitive;
 
 /**
  * Descriptor for {@link Character} handling.
  *
  * @author Steve Ebersole
  */
-public class CharacterTypeDescriptor extends AbstractTypeDescriptor<Character> {
+public class CharacterTypeDescriptor extends AbstractTypeDescriptor<Character> implements Primitive<Character> {
 	public static final CharacterTypeDescriptor INSTANCE = new CharacterTypeDescriptor();
 
 	public CharacterTypeDescriptor() {
@@ -66,4 +67,14 @@ public class CharacterTypeDescriptor extends AbstractTypeDescriptor<Character> {
 		}
 		throw unknownWrap( value.getClass() );
 	}
+
+	@Override
+	public Class getPrimitiveClass() {
+		return char.class;
+	}
+
+	@Override
+	public Character getDefaultValue() {
+		return 0;
+	}
 }

hibernate-core/src/main/java/org/hibernate/type/descriptor/java/DoubleTypeDescriptor.java

@@ -10,13 +10,14 @@ import java.math.BigDecimal;
 import java.math.BigInteger;
 
 import org.hibernate.type.descriptor.WrapperOptions;
+import org.hibernate.type.descriptor.java.spi.Primitive;
 
 /**
  * Descriptor for {@link Double} handling.
  *
  * @author Steve Ebersole
  */
-public class DoubleTypeDescriptor extends AbstractTypeDescriptor<Double> {
+public class DoubleTypeDescriptor extends AbstractTypeDescriptor<Double> implements Primitive<Double> {
 	public static final DoubleTypeDescriptor INSTANCE = new DoubleTypeDescriptor();
 
 	public DoubleTypeDescriptor() {
@@ -71,15 +72,25 @@ public class DoubleTypeDescriptor extends AbstractTypeDescriptor<Double> {
 		if ( value == null ) {
 			return null;
 		}
-		if ( Double.class.isInstance( value ) ) {
+		if ( value instanceof Double ) {
 			return (Double) value;
 		}
-		if ( Number.class.isInstance( value ) ) {
+		if ( value instanceof Number ) {
 			return ( (Number) value ).doubleValue();
 		}
-		else if ( String.class.isInstance( value ) ) {
+		else if ( value instanceof String ) {
 			return Double.valueOf( ( (String) value ) );
 		}
 		throw unknownWrap( value.getClass() );
 	}
+
+	@Override
+	public Class getPrimitiveClass() {
+		return double.class;
+	}
+
+	@Override
+	public Double getDefaultValue() {
+		return 0.0;
+	}
 }

hibernate-core/src/main/java/org/hibernate/type/descriptor/java/FloatTypeDescriptor.java

@@ -10,13 +10,14 @@ import java.math.BigDecimal;
 import java.math.BigInteger;
 
 import org.hibernate.type.descriptor.WrapperOptions;
+import org.hibernate.type.descriptor.java.spi.Primitive;
 
 /**
  * Descriptor for {@link Float} handling.
  *
  * @author Steve Ebersole
  */
-public class FloatTypeDescriptor extends AbstractTypeDescriptor<Float> {
+public class FloatTypeDescriptor extends AbstractTypeDescriptor<Float> implements Primitive<Float> {
 	public static final FloatTypeDescriptor INSTANCE = new FloatTypeDescriptor();
 
 	public FloatTypeDescriptor() {
@@ -82,4 +83,14 @@ public class FloatTypeDescriptor extends AbstractTypeDescriptor<Float> {
 		}
 		throw unknownWrap( value.getClass() );
 	}
+
+	@Override
+	public Class getPrimitiveClass() {
+		return float.class;
+	}
+
+	@Override
+	public Float getDefaultValue() {
+		return 0F;
+	}
 }

hibernate-core/src/main/java/org/hibernate/type/descriptor/java/IntegerTypeDescriptor.java

@@ -10,13 +10,14 @@ import java.math.BigDecimal;
 import java.math.BigInteger;
 
 import org.hibernate.type.descriptor.WrapperOptions;
+import org.hibernate.type.descriptor.java.spi.Primitive;
 
 /**
  * Descriptor for {@link Integer} handling.
  *
  * @author Steve Ebersole
  */
-public class IntegerTypeDescriptor extends AbstractTypeDescriptor<Integer> {
+public class IntegerTypeDescriptor extends AbstractTypeDescriptor<Integer> implements Primitive<Integer> {
 	public static final IntegerTypeDescriptor INSTANCE = new IntegerTypeDescriptor();
 
 	public IntegerTypeDescriptor() {
@@ -82,4 +83,14 @@ public class IntegerTypeDescriptor extends AbstractTypeDescriptor<Integer> {
 		}
 		throw unknownWrap( value.getClass() );
 	}
+
+	@Override
+	public Class getPrimitiveClass() {
+		return int.class;
+	}
+
+	@Override
+	public Integer getDefaultValue() {
+		return 0;
+	}
 }

hibernate-core/src/main/java/org/hibernate/type/descriptor/java/LongTypeDescriptor.java

@@ -10,13 +10,14 @@ import java.math.BigDecimal;
 import java.math.BigInteger;
 
 import org.hibernate.type.descriptor.WrapperOptions;
+import org.hibernate.type.descriptor.java.spi.Primitive;
 
 /**
  * Descriptor for {@link Long} handling.
  *
  * @author Steve Ebersole
  */
-public class LongTypeDescriptor extends AbstractTypeDescriptor<Long> {
+public class LongTypeDescriptor extends AbstractTypeDescriptor<Long>implements Primitive<Long> {
 	public static final LongTypeDescriptor INSTANCE = new LongTypeDescriptor();
 
 	public LongTypeDescriptor() {
@@ -82,4 +83,14 @@ public class LongTypeDescriptor extends AbstractTypeDescriptor<Long> {
 		}
 		throw unknownWrap( value.getClass() );
 	}
+
+	@Override
+	public Class getPrimitiveClass() {
+		return long.class;
+	}
+
+	@Override
+	public Long getDefaultValue() {
+		return 0L;
+	}
 }

hibernate-core/src/main/java/org/hibernate/type/descriptor/java/ShortTypeDescriptor.java

@@ -6,13 +6,14 @@
  */
 package org.hibernate.type.descriptor.java;
 import org.hibernate.type.descriptor.WrapperOptions;
+import org.hibernate.type.descriptor.java.spi.Primitive;
 
 /**
  * Descriptor for {@link Short} handling.
  *
  * @author Steve Ebersole
  */
-public class ShortTypeDescriptor extends AbstractTypeDescriptor<Short> {
+public class ShortTypeDescriptor extends AbstractTypeDescriptor<Short> implements Primitive<Short> {
 	public static final ShortTypeDescriptor INSTANCE = new ShortTypeDescriptor();
 
 	public ShortTypeDescriptor() {
@@ -72,4 +73,14 @@ public class ShortTypeDescriptor extends AbstractTypeDescriptor<Short> {
 		}
 		throw unknownWrap( value.getClass() );
 	}
+
+	@Override
+	public Class getPrimitiveClass() {
+		return short.class;
+	}
+
+	@Override
+	public Short getDefaultValue() {
+		return 0;
+	}
 }

hibernate-core/src/main/java/org/hibernate/type/descriptor/java/spi/JavaTypeDescriptorRegistry.java

@@ -39,6 +39,7 @@ public class JavaTypeDescriptorRegistry implements JavaTypeDescriptorBaseline.Ba
 	@SuppressWarnings("unused")
 	public JavaTypeDescriptorRegistry(TypeConfiguration typeConfiguration) {
 		this.typeConfiguration = typeConfiguration;
+		JavaTypeDescriptorBaseline.prime( this );
 	}
 
 

hibernate-core/src/test/java/org/hibernate/jpa/test/ejb3configuration/PersisterClassProviderTest.java

@@ -21,6 +21,7 @@ import org.hibernate.HibernateException;
 import org.hibernate.LockMode;
 import org.hibernate.LockOptions;
 import org.hibernate.MappingException;
+import org.hibernate.NotYetImplementedFor6Exception;
 import org.hibernate.bytecode.spi.BytecodeEnhancementMetadata;
 import org.hibernate.cache.spi.access.EntityDataAccess;
 import org.hibernate.cache.spi.access.NaturalIdDataAccess;
@@ -58,6 +59,11 @@ import org.hibernate.persister.spi.PersisterClassResolver;
 import org.hibernate.persister.spi.PersisterCreationContext;
 import org.hibernate.persister.walking.spi.AttributeDefinition;
 import org.hibernate.persister.walking.spi.EntityIdentifierDefinition;
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
+import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBase;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
+import org.hibernate.sql.ast.tree.from.TableReferenceCollector;
 import org.hibernate.tuple.entity.BytecodeEnhancementMetadataNonPojoImpl;
 import org.hibernate.tuple.entity.EntityMetamodel;
 import org.hibernate.tuple.entity.EntityTuplizer;
@@ -717,6 +723,16 @@ public class PersisterClassProviderTest {
 		public JavaTypeDescriptor getMappedJavaTypeDescriptor() {
 			return null;
 		}
+
+		@Override
+		public void applyTableReferences(
+				SqlAliasBase sqlAliasBase,
+				JoinType baseJoinType,
+				TableReferenceCollector collector,
+				SqlExpressionResolver sqlExpressionResolver,
+				SqlAstCreationContext creationContext) {
+			throw new NotYetImplementedFor6Exception( getClass() );
+		}
 	}
 
 	public static class GoofyException extends RuntimeException {

hibernate-core/src/test/java/org/hibernate/orm/test/metamodel/mapping/PluralAttributeTests.java

@@ -6,13 +6,16 @@
  */
 package org.hibernate.orm.test.metamodel.mapping;
 
-import java.sql.Statement;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 import javax.persistence.AttributeConverter;
 import javax.persistence.CascadeType;
+import javax.persistence.Convert;
 import javax.persistence.ElementCollection;
 import javax.persistence.Embeddable;
+import javax.persistence.Embedded;
 import javax.persistence.Entity;
 import javax.persistence.EnumType;
 import javax.persistence.Enumerated;
@@ -21,14 +24,20 @@ import javax.persistence.OneToMany;
 import javax.persistence.OrderColumn;
 import javax.persistence.Table;
 
+import org.hibernate.metamodel.mapping.AttributeMapping;
+import org.hibernate.metamodel.mapping.EntityMappingType;
+import org.hibernate.metamodel.spi.DomainMetamodel;
+
 import org.hibernate.testing.orm.junit.DomainModel;
 import org.hibernate.testing.orm.junit.ServiceRegistry;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
-import org.junit.jupiter.api.AfterAll;
-import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.CoreMatchers.notNullValue;
+import static org.hamcrest.MatcherAssert.assertThat;
+
 /**
  * @author Steve Ebersole
  */
@@ -36,6 +45,7 @@ import org.junit.jupiter.api.Test;
 		annotatedClasses = {
 				PluralAttributeTests.SimpleEntity.class,
 				PluralAttributeTests.EntityContainingLists.class,
+				PluralAttributeTests.EntityContainingSets.class,
 				PluralAttributeTests.Component.class
 		}
 )
@@ -46,51 +56,50 @@ public class PluralAttributeTests {
 
 	@Test
 	public void testLists(SessionFactoryScope scope) {
-		System.out.println( "test" );
+		final DomainMetamodel domainModel = scope.getSessionFactory().getDomainModel();
+		final EntityMappingType containerEntityDescriptor = domainModel.getEntityDescriptor( EntityContainingLists.class );
+
+		assertThat( containerEntityDescriptor.getNumberOfAttributeMappings(), is( 6 ) );
+
+		final AttributeMapping listOfBasics = containerEntityDescriptor.findAttributeMapping( "listOfBasics" );
+		assertThat( listOfBasics, notNullValue() );
+
+		final AttributeMapping listOfConvertedBasics = containerEntityDescriptor.findAttributeMapping( "listOfConvertedBasics" );
+		assertThat( listOfConvertedBasics, notNullValue() );
+
+
+		final AttributeMapping listOfEnums = containerEntityDescriptor.findAttributeMapping( "listOfEnums" );
+		assertThat( listOfEnums, notNullValue() );
+
+		final AttributeMapping listOfComponents = containerEntityDescriptor.findAttributeMapping( "listOfComponents" );
+		assertThat( listOfComponents, notNullValue() );
+
+		final AttributeMapping listOfEntities = containerEntityDescriptor.findAttributeMapping( "listOfEntities" );
+		assertThat( listOfEntities, notNullValue() );
 	}
 
-	@BeforeAll
-	public void createTestData(SessionFactoryScope scope) {
-		scope.inTransaction(
-				session -> {
-					final EntityContainingLists entityContainingLists = new EntityContainingLists( 1, "first" );
+	@Test
+	public void testSets(SessionFactoryScope scope) {
+		final DomainMetamodel domainModel = scope.getSessionFactory().getDomainModel();
+		final EntityMappingType containerEntityDescriptor = domainModel.getEntityDescriptor( EntityContainingSets.class );
 
-					entityContainingLists.addBasic( "abc" );
-					entityContainingLists.addBasic( "def" );
-					entityContainingLists.addBasic( "ghi" );
+		assertThat( containerEntityDescriptor.getNumberOfAttributeMappings(), is( 6 ) );
 
-					entityContainingLists.addConvertedBasic( EnumValue.TWO );
+		final AttributeMapping setOfBasics = containerEntityDescriptor.findAttributeMapping( "setOfBasics" );
+		assertThat( setOfBasics, notNullValue() );
 
-					entityContainingLists.addEnum( EnumValue.ONE );
-					entityContainingLists.addEnum( EnumValue.THREE );
+		final AttributeMapping setOfConvertedBasics = containerEntityDescriptor.findAttributeMapping( "setOfConvertedBasics" );
+		assertThat( setOfConvertedBasics, notNullValue() );
 
-					entityContainingLists.addComponent( new Component( "first-a1", "first-another-a1" ) );
-					entityContainingLists.addComponent( new Component( "first-a2", "first-another-a2" ) );
 
-					entityContainingLists.addSimpleEntity( new SimpleEntity( 1, "simple-1" ) );
-					entityContainingLists.addSimpleEntity( new SimpleEntity( 2, "simple-2" ) );
+		final AttributeMapping setOfEnums = containerEntityDescriptor.findAttributeMapping( "setOfEnums" );
+		assertThat( setOfEnums, notNullValue() );
 
-					session.save( entityContainingLists );
-				}
-		);
-	}
+		final AttributeMapping setOfComponents = containerEntityDescriptor.findAttributeMapping( "setOfComponents" );
+		assertThat( setOfComponents, notNullValue() );
 
-	@AfterAll
-	public void deleteTestData(SessionFactoryScope scope) {
-		scope.inTransaction(
-				session -> session.doWork(
-						conn -> {
-							try ( Statement stmnt = conn.createStatement() ) {
-								stmnt.execute( "delete from EntityContainingLists_listOfEnums" );
-								stmnt.execute( "delete from EntityContainingLists_listOfConvertedBasics" );
-								stmnt.execute( "delete from EntityContainingLists_listOfComponents" );
-								stmnt.execute( "delete from EntityContainingLists_listOfBasics" );
-								stmnt.execute( "delete from entity_containing_lists_simple_entity" );
-								stmnt.execute( "delete from entity_containing_lists" );
-							}
-						}
-				)
-		);
+		final AttributeMapping setOfEntities = containerEntityDescriptor.findAttributeMapping( "setOfEntities" );
+		assertThat( setOfEntities, notNullValue() );
 	}
 
 	public enum EnumValue {
@@ -198,6 +207,7 @@ public class PluralAttributeTests {
 
 		@ElementCollection
 		@OrderColumn
+		@Convert( converter = Converter.class )
 		public List<EnumValue> getListOfConvertedBasics() {
 			return listOfConvertedBasics;
 		}
@@ -266,6 +276,127 @@ public class PluralAttributeTests {
 		}
 	}
 
+	@Entity( name = "EntityContainingSets" )
+	@Table( name = "entity_containing_sets" )
+	public static class EntityContainingSets {
+		private Integer id;
+		private String name;
+
+		private Set<String> setOfBasics;
+		private Set<EnumValue> setOfConvertedBasics;
+		private Set<EnumValue> setOfEnums;
+		private Set<Component> setOfComponents;
+		private Set<SimpleEntity> setOfEntities;
+
+		public EntityContainingSets() {
+		}
+
+		public EntityContainingSets(Integer id, String name) {
+			this.id = id;
+			this.name = name;
+		}
+
+		@Id
+		public Integer getId() {
+			return id;
+		}
+
+		public void setId(Integer id) {
+			this.id = id;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+
+		@ElementCollection
+		public Set<String> getSetOfBasics() {
+			return setOfBasics;
+		}
+
+		public void setSetOfBasics(Set<String> setOfBasics) {
+			this.setOfBasics = setOfBasics;
+		}
+
+		public void addBasic(String value) {
+			if ( setOfBasics == null ) {
+				setOfBasics = new HashSet<>();
+			}
+			setOfBasics.add( value );
+		}
+
+		@ElementCollection
+		@Convert( converter = Converter.class )
+		public Set<EnumValue> getSetOfConvertedBasics() {
+			return setOfConvertedBasics;
+		}
+
+		public void setSetOfConvertedBasics(Set<EnumValue> setOfConvertedBasics) {
+			this.setOfConvertedBasics = setOfConvertedBasics;
+		}
+
+		public void addConvertedBasic(EnumValue value) {
+			if ( setOfConvertedBasics == null ) {
+				setOfConvertedBasics = new HashSet<>();
+			}
+			setOfConvertedBasics.add( value );
+		}
+
+		@ElementCollection
+		@Enumerated( EnumType.STRING )
+		public Set<EnumValue> getSetOfEnums() {
+			return setOfEnums;
+		}
+
+		public void setSetOfEnums(Set<EnumValue> setOfEnums) {
+			this.setOfEnums = setOfEnums;
+		}
+
+		public void addEnum(EnumValue value) {
+			if ( setOfEnums == null ) {
+				setOfEnums = new HashSet<>();
+			}
+			setOfEnums.add( value );
+		}
+
+		@ElementCollection
+		@Embedded
+		public Set<Component> getSetOfComponents() {
+			return setOfComponents;
+		}
+
+		public void setSetOfComponents(Set<Component> setOfComponents) {
+			this.setOfComponents = setOfComponents;
+		}
+
+		public void addComponent(Component value) {
+			if ( setOfComponents == null ) {
+				setOfComponents = new HashSet<>();
+			}
+			setOfComponents.add( value );
+		}
+
+		@OneToMany( cascade = CascadeType.ALL )
+		public Set<SimpleEntity> getSetOfEntities() {
+			return setOfEntities;
+		}
+
+		public void setSetOfEntities(Set<SimpleEntity> setOfEntities) {
+			this.setOfEntities = setOfEntities;
+		}
+
+		public void addSimpleEntity(SimpleEntity value) {
+			if ( setOfEntities == null ) {
+				setOfEntities = new HashSet<>();
+			}
+			setOfEntities.add( value );
+		}
+	}
+
 	@Entity( name = "SimpleEntity" )
 	@Table( name = "simple_entity" )
 	public static class SimpleEntity {

hibernate-core/src/test/java/org/hibernate/orm/test/metamodel/mapping/SmokeTests.java

@@ -24,7 +24,10 @@ import org.hibernate.metamodel.mapping.internal.EmbeddedAttributeMapping;
 import org.hibernate.metamodel.mapping.internal.SingularAssociationAttributeMapping;
 import org.hibernate.metamodel.model.convert.internal.NamedEnumValueConverter;
 import org.hibernate.metamodel.model.convert.internal.OrdinalEnumValueConverter;
+import org.hibernate.metamodel.model.convert.spi.EnumValueConverter;
 import org.hibernate.persister.entity.EntityPersister;
+import org.hibernate.type.CustomType;
+import org.hibernate.usertype.UserType;
 
 import org.hibernate.testing.hamcrest.CollectionMatchers;
 import org.hibernate.testing.orm.junit.DomainModel;
@@ -72,8 +75,12 @@ public class SmokeTests {
 			final BasicValuedSingularAttributeMapping genderAttrMapping = (BasicValuedSingularAttributeMapping) genderPart;
 			assert "mapping_simple_entity".equals( genderAttrMapping.getContainingTableExpression() );
 			assert "gender".equals( genderAttrMapping.getMappedColumnExpression() );
-			assert genderAttrMapping.getConverter() != null;
-			assert genderAttrMapping.getConverter() instanceof OrdinalEnumValueConverter;
+			assert genderAttrMapping.getMappedTypeDescriptor() instanceof CustomType;
+			final UserType userType = ( (CustomType) genderAttrMapping.getMappedTypeDescriptor() ).getUserType();
+			assert userType instanceof org.hibernate.type.EnumType;
+			final EnumValueConverter converter = ( (org.hibernate.type.EnumType) userType ).getEnumValueConverter();
+			assert converter != null;
+			assert converter instanceof OrdinalEnumValueConverter;
 		}
 
 		{
@@ -82,8 +89,13 @@ public class SmokeTests {
 			final BasicValuedSingularAttributeMapping attrMapping = (BasicValuedSingularAttributeMapping) part;
 			assert "mapping_simple_entity".equals( attrMapping.getContainingTableExpression() );
 			assert "gender2".equals( attrMapping.getMappedColumnExpression() );
-			assert attrMapping.getConverter() != null;
-			assert attrMapping.getConverter() instanceof NamedEnumValueConverter;
+
+			assert attrMapping.getMappedTypeDescriptor() instanceof CustomType;
+			final UserType userType = ( (CustomType) attrMapping.getMappedTypeDescriptor() ).getUserType();
+			assert userType instanceof org.hibernate.type.EnumType;
+			final EnumValueConverter converter = ( (org.hibernate.type.EnumType) userType ).getEnumValueConverter();
+			assert converter != null;
+			assert converter instanceof NamedEnumValueConverter;
 		}
 
 		{

hibernate-core/src/test/java/org/hibernate/orm/test/sql/ast/SmokeTests.java

@@ -35,7 +35,10 @@ import org.hibernate.sql.results.internal.domain.basic.BasicResult;
 import org.hibernate.sql.results.internal.SqlSelectionImpl;
 import org.hibernate.sql.results.spi.DomainResult;
 import org.hibernate.sql.results.spi.DomainResultAssembler;
+import org.hibernate.type.CustomType;
+import org.hibernate.type.EnumType;
 import org.hibernate.type.internal.StandardBasicTypeImpl;
+import org.hibernate.usertype.UserType;
 
 import org.hibernate.testing.hamcrest.AssignableMatcher;
 import org.hibernate.testing.orm.junit.DomainModel;
@@ -49,6 +52,7 @@ import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.CoreMatchers.notNullValue;
+import static org.hamcrest.CoreMatchers.nullValue;
 import static org.hamcrest.MatcherAssert.assertThat;
 
 /**
@@ -174,10 +178,15 @@ public class SmokeTests {
 					assertThat( columnReference.renderSqlFragment( scope.getSessionFactory() ), is( "s1_0.gender" ) );
 
 					final MappingModelExpressable selectedExpressable = selectedExpression.getExpressionType();
-					assertThat( selectedExpressable, instanceOf( StandardBasicTypeImpl.class ) );
-					final StandardBasicTypeImpl basicType = (StandardBasicTypeImpl) selectedExpressable;
-					assertThat( basicType.getJavaTypeDescriptor().getJavaType(), AssignableMatcher.assignableTo( Integer.class ) );
-					assertThat( basicType.getSqlTypeDescriptor().getSqlType(), is( Types.INTEGER ) );
+					//assertThat( selectedExpressable, instanceOf( StandardBasicTypeImpl.class ) );
+//					assertThat( basicType.getJavaTypeDescriptor().getJavaType(), AssignableMatcher.assignableTo( Integer.class ) );
+//					assertThat( basicType.getSqlTypeDescriptor().getSqlType(), is( Types.INTEGER ) );
+					assertThat( selectedExpressable, instanceOf( CustomType.class ) );
+					final CustomType basicType = (CustomType) selectedExpressable;
+					final EnumType enumType = (EnumType) basicType.getUserType();
+					assertThat( enumType.getEnumValueConverter().getRelationalJavaDescriptor().getJavaType(), AssignableMatcher.assignableTo( Integer.class ) );
+					assertThat( enumType.sqlTypes()[0], is( Types.INTEGER ) );
+
 
 					assertThat( sqlAst.getDomainResultDescriptors().size(), is( 1 ) );
 					final DomainResult domainResult = sqlAst.getDomainResultDescriptors().get( 0 );
@@ -185,8 +194,10 @@ public class SmokeTests {
 					final BasicResult scalarDomainResult = (BasicResult) domainResult;
 					assertThat( scalarDomainResult.getAssembler(), instanceOf( BasicResultAssembler.class ) );
 					final BasicResultAssembler<?> assembler = (BasicResultAssembler) scalarDomainResult.getAssembler();
-					assertThat( assembler.getValueConverter(), notNullValue() );
-					assertThat( assembler.getValueConverter(), instanceOf( OrdinalEnumValueConverter.class ) );
+//					assertThat( assembler.getValueConverter(), notNullValue() );
+//					assertThat( assembler.getValueConverter(), instanceOf( OrdinalEnumValueConverter.class ) );
+					assertThat( assembler.getValueConverter(), nullValue() );
+
 					final NavigablePath expectedSelectedPath = new NavigablePath(
 							org.hibernate.orm.test.metamodel.mapping.SmokeTests.SimpleEntity.class.getName(),
 							"e"
@@ -202,9 +213,10 @@ public class SmokeTests {
 					);
 
 					assertThat( resultAssembler, instanceOf( BasicResultAssembler.class ) );
-					final BasicValueConverter valueConverter = ( (BasicResultAssembler) resultAssembler ).getValueConverter();
-					assertThat( valueConverter, notNullValue() );
-					assertThat( valueConverter, instanceOf( OrdinalEnumValueConverter.class ) );
+//					final BasicValueConverter valueConverter = ( (BasicResultAssembler) resultAssembler ).getValueConverter();
+//					assertThat( valueConverter, notNullValue() );
+//					assertThat( valueConverter, instanceOf( OrdinalEnumValueConverter.class ) );
+					assertThat( ( (BasicResultAssembler) resultAssembler ).getValueConverter(), nullValue() );
 
 					final JdbcSelect jdbcSelectOperation = new StandardSqlAstSelectTranslator( session.getSessionFactory() )
 							.interpret( sqlAst );

hibernate-core/src/test/java/org/hibernate/orm/test/sql/exec/PluralAttributeSmokeTests.java

@@ -0,0 +1,196 @@
+/*
+ * 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.sql.exec;
+
+import java.sql.Statement;
+
+import org.hibernate.Hibernate;
+import org.hibernate.collection.spi.PersistentCollection;
+import org.hibernate.orm.test.metamodel.mapping.PluralAttributeTests.Component;
+import org.hibernate.orm.test.metamodel.mapping.PluralAttributeTests.EntityContainingLists;
+import org.hibernate.orm.test.metamodel.mapping.PluralAttributeTests.EntityContainingSets;
+import org.hibernate.orm.test.metamodel.mapping.PluralAttributeTests.EnumValue;
+import org.hibernate.orm.test.metamodel.mapping.PluralAttributeTests.SimpleEntity;
+import org.hibernate.query.spi.QueryImplementor;
+
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.ServiceRegistry;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import org.hamcrest.CoreMatchers;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.CoreMatchers.notNullValue;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * @author Steve Ebersole
+ */
+@DomainModel(
+		annotatedClasses = {
+				SimpleEntity.class,
+				EntityContainingLists.class,
+				EntityContainingSets.class,
+				Component.class
+		}
+)
+@ServiceRegistry
+@SessionFactory
+@SuppressWarnings("WeakerAccess")
+public class PluralAttributeSmokeTests {
+
+	@Test
+	public void listBaselineTest(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					final QueryImplementor<EntityContainingLists> query = session.createQuery(
+							"select e from EntityContainingLists e",
+							EntityContainingLists.class
+					);
+					final EntityContainingLists result = query.uniqueResult();
+
+					assertThat( result, notNullValue() );
+					assertThat( result.getListOfBasics(), notNullValue() );
+					assertThat( Hibernate.isInitialized( result.getListOfBasics() ), is( false ) );
+				}
+		);
+	}
+
+	@Test
+	public void listEagerBasicTest(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					final QueryImplementor<EntityContainingLists> query = session.createQuery(
+							"select e from EntityContainingLists e join fetch e.listOfBasics",
+							EntityContainingLists.class
+					);
+					final EntityContainingLists result = query.uniqueResult();
+
+					assertThat( result, notNullValue() );
+
+					assertThat( result.getListOfBasics(), notNullValue() );
+					assertThat( Hibernate.isInitialized( result.getListOfBasics() ), is( true ) );
+					assertTrue( session.getPersistenceContext().containsCollection( (PersistentCollection) result.getListOfBasics() ) );
+					assertThat( result.getListOfBasics().size(), is( 3 ) );
+
+					assertThat( result.getListOfConvertedBasics(), notNullValue() );
+					assertThat( Hibernate.isInitialized( result.getListOfConvertedBasics() ), is( false ) );
+					assertTrue( session.getPersistenceContext().containsCollection( (PersistentCollection) result.getListOfConvertedBasics() ) );
+
+					assertThat( result.getListOfEnums(), notNullValue() );
+					assertThat( Hibernate.isInitialized( result.getListOfEnums() ), is( false ) );
+					assertTrue( session.getPersistenceContext().containsCollection( (PersistentCollection) result.getListOfEnums() ) );
+
+					assertThat( result.getListOfComponents(), notNullValue() );
+					assertThat( Hibernate.isInitialized( result.getListOfComponents() ), is( false ) );
+					assertTrue( session.getPersistenceContext().containsCollection( (PersistentCollection) result.getListOfComponents() ) );
+
+					assertThat( result.getListOfEntities(), notNullValue() );
+					assertThat( Hibernate.isInitialized( result.getListOfEntities() ), is( false ) );
+					assertTrue( session.getPersistenceContext().containsCollection( (PersistentCollection) result.getListOfEntities() ) );
+
+				}
+		);
+	}
+
+	@Test
+	public void setBaselineTest(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					final QueryImplementor<EntityContainingSets> query = session.createQuery(
+							"select e from EntityContainingSets e",
+							EntityContainingSets.class
+					);
+
+					final EntityContainingSets result = query.uniqueResult();
+
+					assertThat( result, notNullValue() );
+					assertThat( result.getSetOfBasics(), notNullValue() );
+					assertThat( Hibernate.isInitialized( result.getSetOfBasics() ), is( false ) );
+				}
+		);
+	}
+
+
+	@BeforeAll
+	public void createTestData(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> {
+					final SimpleEntity simpleEntity1 = new SimpleEntity( 1, "simple-1" );
+					final SimpleEntity simpleEntity2 = new SimpleEntity( 2, "simple-2" );
+
+					session.save( simpleEntity1 );
+					session.save( simpleEntity2 );
+
+					{
+						final EntityContainingLists entityContainingLists = new EntityContainingLists( 1, "first" );
+
+						entityContainingLists.addBasic( "abc" );
+						entityContainingLists.addBasic( "def" );
+						entityContainingLists.addBasic( "ghi" );
+
+						entityContainingLists.addConvertedBasic( EnumValue.TWO );
+
+						entityContainingLists.addEnum( EnumValue.ONE );
+						entityContainingLists.addEnum( EnumValue.THREE );
+
+						entityContainingLists.addComponent( new Component( "first-a1", "first-another-a1" ) );
+						entityContainingLists.addComponent( new Component( "first-a2", "first-another-a2" ) );
+
+						entityContainingLists.addSimpleEntity( simpleEntity1 );
+						entityContainingLists.addSimpleEntity( simpleEntity2 );
+
+						session.save( entityContainingLists );
+					}
+
+					{
+						final EntityContainingSets entity = new EntityContainingSets( 1, "first" );
+
+						entity.addBasic( "abc" );
+						entity.addBasic( "def" );
+						entity.addBasic( "ghi" );
+
+						entity.addConvertedBasic( EnumValue.TWO );
+
+						entity.addEnum( EnumValue.ONE );
+						entity.addEnum( EnumValue.THREE );
+
+						entity.addComponent( new Component( "first-a1", "first-another-a1" ) );
+						entity.addComponent( new Component( "first-a2", "first-another-a2" ) );
+
+						entity.addSimpleEntity( simpleEntity1 );
+						entity.addSimpleEntity( simpleEntity2 );
+
+						session.save( entity );
+					}
+				}
+		);
+	}
+
+	@AfterAll
+	public void deleteTestData(SessionFactoryScope scope) {
+		scope.inTransaction(
+				session -> session.doWork(
+						conn -> {
+							try ( Statement stmnt = conn.createStatement() ) {
+								stmnt.execute( "delete from EntityContainingLists_listOfEnums" );
+								stmnt.execute( "delete from EntityContainingLists_listOfConvertedBasics" );
+								stmnt.execute( "delete from EntityContainingLists_listOfComponents" );
+								stmnt.execute( "delete from EntityContainingLists_listOfBasics" );
+								stmnt.execute( "delete from entity_containing_lists_simple_entity" );
+								stmnt.execute( "delete from entity_containing_lists" );
+							}
+						}
+				)
+		);
+	}
+}

hibernate-core/src/test/java/org/hibernate/orm/test/sql/exec/SmokeTests.java

@@ -12,7 +12,6 @@ import java.util.List;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 
 import org.hibernate.cfg.AvailableSettings;

hibernate-core/src/test/java/org/hibernate/test/cfg/persister/GoofyPersisterClassProvider.java

@@ -20,6 +20,7 @@ import org.hibernate.HibernateException;
 import org.hibernate.LockMode;
 import org.hibernate.LockOptions;
 import org.hibernate.MappingException;
+import org.hibernate.NotYetImplementedFor6Exception;
 import org.hibernate.bytecode.spi.BytecodeEnhancementMetadata;
 import org.hibernate.cache.spi.access.CollectionDataAccess;
 import org.hibernate.cache.spi.access.EntityDataAccess;
@@ -58,6 +59,11 @@ import org.hibernate.persister.walking.spi.AttributeDefinition;
 import org.hibernate.persister.walking.spi.CollectionElementDefinition;
 import org.hibernate.persister.walking.spi.CollectionIndexDefinition;
 import org.hibernate.persister.walking.spi.EntityIdentifierDefinition;
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
+import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBase;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
+import org.hibernate.sql.ast.tree.from.TableReferenceCollector;
 import org.hibernate.tuple.entity.BytecodeEnhancementMetadataNonPojoImpl;
 import org.hibernate.tuple.entity.EntityMetamodel;
 import org.hibernate.tuple.entity.EntityTuplizer;
@@ -703,6 +709,16 @@ public class GoofyPersisterClassProvider implements PersisterClassResolver {
 		public JavaTypeDescriptor getMappedJavaTypeDescriptor() {
 			return null;
 		}
+
+		@Override
+		public void applyTableReferences(
+				SqlAliasBase sqlAliasBase,
+				JoinType baseJoinType,
+				TableReferenceCollector collector,
+				SqlExpressionResolver sqlExpressionResolver,
+				SqlAstCreationContext creationContext) {
+			throw new NotYetImplementedFor6Exception( getClass() );
+		}
 	}
 
 	public static class NoopCollectionPersister implements CollectionPersister {

hibernate-core/src/test/java/org/hibernate/test/legacy/CustomPersister.java

@@ -21,6 +21,7 @@ import org.hibernate.HibernateException;
 import org.hibernate.LockMode;
 import org.hibernate.LockOptions;
 import org.hibernate.MappingException;
+import org.hibernate.NotYetImplementedFor6Exception;
 import org.hibernate.bytecode.spi.BytecodeEnhancementMetadata;
 import org.hibernate.cache.spi.access.EntityDataAccess;
 import org.hibernate.cache.spi.access.NaturalIdDataAccess;
@@ -59,6 +60,11 @@ import org.hibernate.persister.entity.MultiLoadOptions;
 import org.hibernate.persister.spi.PersisterCreationContext;
 import org.hibernate.persister.walking.spi.AttributeDefinition;
 import org.hibernate.persister.walking.spi.EntityIdentifierDefinition;
+import org.hibernate.query.sqm.sql.SqlExpressionResolver;
+import org.hibernate.sql.ast.JoinType;
+import org.hibernate.sql.ast.spi.SqlAliasBase;
+import org.hibernate.sql.ast.spi.SqlAstCreationContext;
+import org.hibernate.sql.ast.tree.from.TableReferenceCollector;
 import org.hibernate.tuple.entity.BytecodeEnhancementMetadataNonPojoImpl;
 import org.hibernate.tuple.entity.EntityMetamodel;
 import org.hibernate.tuple.entity.EntityTuplizer;
@@ -815,4 +821,14 @@ public class CustomPersister implements EntityPersister {
 	public JavaTypeDescriptor getMappedJavaTypeDescriptor() {
 		return null;
 	}
+
+	@Override
+	public void applyTableReferences(
+			SqlAliasBase sqlAliasBase,
+			JoinType baseJoinType,
+			TableReferenceCollector collector,
+			SqlExpressionResolver sqlExpressionResolver,
+			SqlAstCreationContext creationContext) {
+		throw new NotYetImplementedFor6Exception( getClass() );
+	}
 }