docs: static byte[] getValueId(final TSDB tsdb, final byte[] row,
                             final byte[] tag_id) {
      final short name_width = tsdb.tag_names.width();
      final short value_width = tsdb.tag_values.width();
      // TODO(tsuna): Can do a binary search.
      for (short pos = (short) (Const.SALT_WIDTH() + 
          tsdb.metrics.width() + Const.TIMESTAMP_BYTES);
           pos < row.length;
           pos += name_width + value_width) {
        if (rowContains(row, pos, tag_id)) {
          pos += name_width;
          return Arrays.copyOfRange(row, pos, pos + value_width);
        }
      }
      return null;
    }