private static void setReadColumnIDConf(Configuration conf, String id) {
    if (id.trim().isEmpty()) {
      conf.set(READ_COLUMN_IDS_CONF_STR, READ_COLUMN_IDS_CONF_STR_DEFAULT);
    } else {
      conf.set(READ_COLUMN_IDS_CONF_STR, id);
    }
  }
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