code: protected void remapFilteredList(final List filteredList) {
          rowNumbers = new HashMap<>(rowMap.size());
          final FacesContext context = FacesContext.getCurrentInstance();
          final Map<String, Object> requestMap = context.getExternalContext().getRequestMap();
          final String var = getVar();
          int row = 0;
          for (final Object value : filteredList) {
              requestMap.put(var, value);
              rowNumbers.put(getRowKeyValueAsString(context), Integer.valueOf(row));
              row++;
          }
          requestMap.remove(var);
      }
docs: Remaps the row keys in a hash map.