code: @Override
      public int getDiscardedResultsCount() {
          if (queryResults instanceof DiscardingBlockingQueue) {
              DiscardingBlockingQueue discardingBlockingQueue = (DiscardingBlockingQueue) queryResults;
              return discardingBlockingQueue.getDiscardedElementCount();
          } else {
              return -1;
          }
      }
docs: Returns the number of discarded elements in the {@link #queryResults} queue
  or <code>-1</code> if the queue is not a {@link DiscardingBlockingQueue}.