code: public Deferred<ArrayList<Object>> flush() {
      final int size = size();
      if (size > 0) {
        LOG.info("Flushing all old outstanding rows out of " + size + " rows");
      }
      final long now = System.currentTimeMillis();
      return flush(now / 1000 - Const.MAX_TIMESPAN - 1, Integer.MAX_VALUE);
    }
docs: Forces a flush of the all old entries in the compaction queue.
  @return A deferred that will be called back once everything has been
  flushed (or something failed, in which case the deferred will carry the
  exception).  In case of success, the kind of object returned is
  unspecified.