[#1517] Fix DefaultReactiveDeleteEventListener

It was executing some operations in parallel because the stages were
created in ahead of time.

Author: DavideD

hibernate-reactive-core/src/main/java/org/hibernate/reactive/event/impl/DefaultReactiveDeleteEventListener.java

@@ -339,59 +339,55 @@ protected CompletionStage<Void> deleteEntity(
 		persistenceContext.setEntryStatus( entityEntry, Status.DELETED );
 		final EntityKey key = session.generateEntityKey( entityEntry.getId(), persister );
 
-		CompletionStage<Void> beforeDelete = cascadeBeforeDelete( session, persister, entity, entityEntry, transientEntities );
-
-		CompletionStage<Void> nullifyAndAction = new ForeignKeys.Nullifier(
-				entity,
-				true,
-				false,
-				session,
-				persister
-		).nullifyTransientReferences( entityEntry.getDeletedState() )
-				.thenAccept( v -> {
-					new Nullability( session ).checkNullability(
-							entityEntry.getDeletedState(),
-							persister,
-							Nullability.NullabilityCheckType.DELETE
-					);
-					persistenceContext.registerNullifiableEntityKey( key );
-
-					ReactiveActionQueue actionQueue = actionQueue( session );
-
-					if ( isOrphanRemovalBeforeUpdates ) {
-						// TODO: The removeOrphan concept is a temporary "hack" for HHH-6484.  This should be removed once action/task
-						// ordering is improved.
-						actionQueue.addAction(
-								new ReactiveOrphanRemovalAction(
-										entityEntry.getId(),
-										deletedState,
-										version,
-										entity,
-										persister,
-										isCascadeDeleteEnabled,
-										session
-								)
-						);
-					}
-					else {
-						// Ensures that containing deletions happen before sub-deletions
-						actionQueue.addAction(
-								new ReactiveEntityDeleteAction(
-										entityEntry.getId(),
-										deletedState,
-										version,
-										entity,
-										persister,
-										isCascadeDeleteEnabled,
-										session
-								)
-						);
-					}
-				} );
-
-		CompletionStage<Void> afterDelete = cascadeAfterDelete( session, persister, entity, transientEntities );
-
-		return beforeDelete.thenCompose( v -> nullifyAndAction ).thenCompose( v -> afterDelete );
+		return cascadeBeforeDelete( session, persister, entity, entityEntry, transientEntities )
+				.thenCompose( v -> new ForeignKeys.Nullifier(
+						entity,
+						true,
+						false,
+						session,
+						persister
+				).nullifyTransientReferences( entityEntry.getDeletedState() )
+						.thenAccept( vv -> {
+							new Nullability( session ).checkNullability(
+									entityEntry.getDeletedState(),
+									persister,
+									Nullability.NullabilityCheckType.DELETE
+							);
+							persistenceContext.registerNullifiableEntityKey( key );
+
+							ReactiveActionQueue actionQueue = actionQueue( session );
+
+							if ( isOrphanRemovalBeforeUpdates ) {
+								// TODO: The removeOrphan concept is a temporary "hack" for HHH-6484.  This should be removed once action/task
+								// ordering is improved.
+								actionQueue.addAction(
+										new ReactiveOrphanRemovalAction(
+												entityEntry.getId(),
+												deletedState,
+												version,
+												entity,
+												persister,
+												isCascadeDeleteEnabled,
+												session
+										)
+								);
+							}
+							else {
+								// Ensures that containing deletions happen before sub-deletions
+								actionQueue.addAction(
+										new ReactiveEntityDeleteAction(
+												entityEntry.getId(),
+												deletedState,
+												version,
+												entity,
+												persister,
+												isCascadeDeleteEnabled,
+												session
+										)
+								);
+							}
+						} ) )
+				.thenCompose( v -> cascadeAfterDelete( session, persister, entity, transientEntities ) );
 	}
 
 	private ReactiveActionQueue actionQueue(EventSource session) {