code: private void getCurrentValuesFromCFS(List<CounterUpdateCell> counterUpdateCells,
                                           ColumnFamilyStore cfs,
                                           ClockAndCount[] currentValues)
      {
          SortedSet<CellName> names = new TreeSet<>(cfs.metadata.comparator);
          for (int i = 0; i < currentValues.length; i++)
              if (currentValues[i] == null)
                  names.add(counterUpdateCells.get(i).name());
  
          ReadCommand cmd = new SliceByNamesReadCommand(getKeyspaceName(), key(), cfs.metadata.cfName, Long.MIN_VALUE, new NamesQueryFilter(names));
          Row row = cmd.getRow(cfs.keyspace);
          ColumnFamily cf = row == null ? null : row.cf;
  
          for (int i = 0; i < currentValues.length; i++)
          {
              if (currentValues[i] != null)
                  continue;
  
              Cell cell = cf == null ? null : cf.getColumn(counterUpdateCells.get(i).name());
              if (cell == null || !cell.isLive()) // absent or a tombstone.
                  currentValues[i] = ClockAndCount.BLANK;
              else
                  currentValues[i] = CounterContext.instance().getLocalClockAndCount(cell.value());
          }
      }
docs: Reads the missing current values from the CFS.