@Override
  protected List<TypeInfo> parseColumnTypes() {
    final List<TypeInfo> fieldTypes = super.parseColumnTypes();
    if (fieldTypes.isEmpty()) {
      return Collections.nCopies(getColumnNames().size(), TypeInfoFactory.stringTypeInfo);
    }
    return fieldTypes;
  }
NOTE: if {@link serdeConstants#LIST_COLUMN_TYPES} is missing, all columns will be of String type.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/OrcSerde.java