private String convertOrcTypeToFieldType(TypeDescription fieldType) {
    if (fieldType.getCategory().isPrimitive()) {
      return convertPrimitiveType(fieldType);
    }
    return convertComplexType(fieldType);
  }
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