HHH-9268 The NoopOptimizer used for default id generation doesn't need synchronization

hibernate-core/src/main/java/org/hibernate/id/enhanced/OptimizerFactory.java

@@ -236,22 +236,23 @@ public class OptimizerFactory {
 	 * An optimizer that performs no optimization.  The database is hit for
 	 * every request.
 	 *
-	 * @deprecated This is the fallback Optimizer chosen when we fail to instantiate one
-	 * of the proper implementations. Using this implementation is probably a performance
-	 * problem.
+	 * Using this implementation is probably not the most efficient choice.
 	 */
-	@Deprecated
 	public static final class NoopOptimizer extends OptimizerSupport {
-		private volatile IntegralDataTypeHolder lastSourceValue;
+		private IntegralDataTypeHolder lastSourceValue;
 
 		public NoopOptimizer(Class returnClass, int incrementSize) {
 			super( returnClass, incrementSize );
 		}
 
 		@Override
-		public synchronized Serializable generate(AccessCallback callback) {
-			// IMPL NOTE : it is incredibly important that the method-local variable be used here to
-			//		avoid concurrency issues.
+		public Serializable generate(AccessCallback callback) {
+			// IMPL NOTE : this method is called concurrently and is
+			// not synchronized. It is very important to work on the
+			// local variable: the field lastSourceValue is not
+			// reliable as it might be mutated by multipled threads.
+			// The lastSourceValue field is only accessed by tests,
+			// so this is not a concern.
 			IntegralDataTypeHolder value = null;
 			while ( value == null || value.lt( 1 ) ) {
 				value = callback.getNextValue();