public static List<Integer> getReadColumnIDs(Configuration conf) {
    String skips = conf.get(READ_COLUMN_IDS_CONF_STR, READ_COLUMN_IDS_CONF_STR_DEFAULT);
    String[] list = StringUtils.split(skips);
    List<Integer> result = new ArrayList<Integer>(list.length);
    for (String element : list) {
      // it may contain duplicates, remove duplicates
      Integer toAdd = Integer.parseInt(element);
      if (!result.contains(toAdd)) {
        result.add(toAdd);
      }
      // NOTE: some code uses this list to correlate with column names, and yet these lists may
      //       contain duplicates, which this call will remove and the other won't. As far as I can
      //       tell, no code will actually use these two methods together; all is good if the code
      //       gets the ID list without relying on this method. Or maybe it just works by magic.
    }
    return result;
  }
Returns an array of column ids(start from zero) which is set in the given
parameter <pre>conf</pre>.
serde/src/java/org/apache/hadoop/hive/serde2/ColumnProjectionUtils.java