code: @Timed(name = "bv.emodb.sor.AstyanaxDataWriterDAO.compact", absolute = true)
      @Override
      public void compact(Table tbl, String key, UUID compactionKey, Compaction compaction, UUID changeId,
                          Delta delta, Collection<DeltaClusteringKey> changesToDelete, List<History> historyList, WriteConsistency consistency) {
          // delegate to CQL Writer for double compaction writing
          _cqlWriterDAO.compact(tbl, key, compactionKey, compaction, changeId, delta, changesToDelete, historyList, consistency);
      }
docs: We need to make sure that compaction is written *before* the compacted deltas are deleted.
  This should be a synchronous operation.