Fix issue with DatabaseSnapshotExecutor not returning the correct array

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

@@ -43,7 +43,7 @@ import org.hibernate.sql.exec.spi.JdbcParameterBindings;
 import org.hibernate.sql.exec.spi.JdbcSelect;
 import org.hibernate.sql.results.graph.DomainResult;
 import org.hibernate.sql.results.graph.basic.BasicResult;
-import org.hibernate.sql.results.internal.RowTransformerPassThruImpl;
+import org.hibernate.sql.results.internal.RowTransformerDatabaseSnapshotImpl;
 
 import org.jboss.logging.Logger;
 
@@ -242,7 +242,7 @@ class DatabaseSnapshotExecutor {
 						return null;
 					}
 				},
-				RowTransformerPassThruImpl.instance(),
+				RowTransformerDatabaseSnapshotImpl.instance(),
 				true
 		);
 
@@ -251,12 +251,14 @@ class DatabaseSnapshotExecutor {
 		}
 
 		final int size = list.size();
-		final Object[] values = new Object[size];
+		assert size <= 1;
-		for ( int i = 0; i < size; i++ ) {
-			values[i] = list.get( i );
-		}
 
-		return values;
+		if ( size == 0 ) {
+			return null;
+		}
+		else {
+			return (Object[]) list.get( 0 );
+		}
 	}
 
 }

hibernate-core/src/main/java/org/hibernate/mapping/Collection.java

@@ -673,7 +673,7 @@ public abstract class Collection implements Fetchable, Value, Filterable {
 
 	@Override
 	public boolean hasAnyUpdatableColumns() {
-		return true;
+		return false;
 	}
 
 	public boolean isSubselectLoadable() {

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

@@ -14,6 +14,7 @@ import org.hibernate.mapping.ManyToOne;
 import org.hibernate.mapping.OneToOne;
 import org.hibernate.mapping.ToOne;
 import org.hibernate.metamodel.mapping.AssociationKey;
+import org.hibernate.metamodel.mapping.ColumnConsumer;
 import org.hibernate.metamodel.mapping.EntityAssociationMapping;
 import org.hibernate.metamodel.mapping.EntityMappingType;
 import org.hibernate.metamodel.mapping.ForeignKeyDescriptor;
@@ -612,4 +613,11 @@ public class ToOneAttributeMapping extends AbstractSingularAttributeMapping
 	public String toString() {
 		return "SingularAssociationAttributeMapping {" + navigableRole + "}";
 	}
+
+	@Override
+	public void visitColumns(ColumnConsumer consumer) {
+		if ( foreignKeyDirection == ForeignKeyDirection.FROM_PARENT ) {
+			foreignKeyDescriptor.visitReferringColumns( consumer );
+		}
+	}
 }

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

@@ -0,0 +1,33 @@
+/*
+ * 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 org.hibernate.sql.results.spi.RowTransformer;
+
+/**
+ * @author Andrea Boriero
+ */
+public class RowTransformerDatabaseSnapshotImpl<T> implements RowTransformer<T> {
+	/**
+	 * Singleton access
+	 */
+	public static final RowTransformerDatabaseSnapshotImpl INSTANCE = new RowTransformerDatabaseSnapshotImpl();
+
+	@SuppressWarnings("unchecked")
+	public static <T> RowTransformerDatabaseSnapshotImpl<T> instance() {
+		return INSTANCE;
+	}
+
+	private RowTransformerDatabaseSnapshotImpl() {
+	}
+
+	@Override
+	@SuppressWarnings("unchecked")
+	public T transformRow(Object[] row) {
+		return (T) row;
+	}
+}