code: public static long getVersionRetroactively(PendingCompaction pendingCompaction) {
          Compaction compaction = pendingCompaction.getCompaction();
          // Calculate the version and create a dummy compaction record for the resolver
          return compaction.getCount() - (long)pendingCompaction.getDeltasToArchive().size();
      }
docs: Find the version of the first delta of a pending compaction retroactively