code: private void reduceNameFilter(QueryFilter filter, ColumnFamily container, long sstableTimestamp)
      {
          if (container == null)
              return;
  
          for (Iterator<CellName> iterator = ((NamesQueryFilter) filter.filter).columns.iterator(); iterator.hasNext(); )
          {
              CellName filterColumn = iterator.next();
              Cell cell = container.getColumn(filterColumn);
              if (cell != null && cell.timestamp() > sstableTimestamp)
                  iterator.remove();
          }
      }
docs: remove columns from @param filter where we already have data in @param container newer than @param sstableTimestamp