pig/src/main/java/com/twitter/elephantbird/pig/util/ThriftToPig.java
private static Schema singleFieldToTupleSchema(String fieldName, Field field) throws FrontendException {
    switch (field.getType()) {
      case TType.STRUCT:
        return wrapInTupleIfPig9(toSchema(field.gettStructDescriptor()));
      case TType.LIST:
      case TType.SET:
      case TType.MAP:
        return wrapInTupleIfPig9(new Schema(singleFieldToFieldSchema(fieldName, field)));
      default:
        return wrapInTupleIfPig9(new Schema(new FieldSchema(fieldName, null, getPigDataType(field))));
    }
  }
private static Schema singleFieldToTupleSchema(String fieldName, Field field) throws FrontendException {
    switch (field.getType()) {
      case TType.STRUCT:
        return wrapInTupleIfPig9(toSchema(field.gettStructDescriptor()));
      case TType.LIST:
      case TType.SET:
      case TType.MAP:
        return wrapInTupleIfPig9(new Schema(singleFieldToFieldSchema(fieldName, field)));
      default:
        return wrapInTupleIfPig9(new Schema(new FieldSchema(fieldName, null, getPigDataType(field))));
    }
  }
Returns a schema with single tuple (for Pig bags).