public void flush() {
   switch (mode) {
     case StreamListener.STORE:
       engine.flush();
       break;
     case StreamListener.REMOVE_ALL_NODES:
       engine.dropIndex(document);
       break;
     case StreamListener.REMOVE_SOME_NODES:
       engine.remove();
       break;
   }
 }
 public void removeCollection(Collection collection, DBBroker broker) {
   engine.dropIndex(collection);
 }