private static String[] extractNeededColNames(
      List<OrcProto.Type> types, Configuration conf, boolean[] include, boolean isOriginal) {
    String colNames = getNeededColumnNamesString(conf);
    if (colNames == null) {
      return null;
    }
    return extractNeededColNames(types, colNames, include, isOriginal);
  }
Take the configuration and figure out which columns we need to include.
@param readerSchema the types for the reader
@param conf the configuration
ql/src/java/org/apache/hadoop/hive/ql/io/orc/OrcInputFormat.java