code: public static long getFirstShortInProgress(Map<Long, TransactionManager.InProgressTx> inProgress) {
      long firstShort = Transaction.NO_TX_IN_PROGRESS;
      for (Map.Entry<Long, TransactionManager.InProgressTx> entry : inProgress.entrySet()) {
        if (!entry.getValue().isLongRunning()) {
          firstShort = entry.getKey();
          break;
        }
      }
      return firstShort;
    }
docs: Returns the write pointer for the first "short" transaction that in the in-progress set, or
  {@link Transaction#NO_TX_IN_PROGRESS} if none.