I don't seem to be able to serialize Thrift structures that contain a Thrift union type (TUnion). An AvroRuntimeException saying "Unknown datum type" is thrown when it gets to that field. Are Thrift unions intended to be supported? It looks like org.apache.avro.thrift.ThriftData#isRecord returns false if the datum is a TUnion and so it falls through all the datum type checks. On the other hand, an Avro schema can be generated for the Thrift class that produces an Avro record type for the TUnion just as if it were a regular TBase struct. I'd expect an error generating the schema if the type was unsupported.
