On Fri, 6 Dec 2019 at 10:38, Ryan Skraba <r...@skraba.com> wrote: > Hello! I had a Java unit test ready to go (looking at default values > for complex types for AVRO-2636), so just reporting back (the easy > work!): >
Thanks for the responses! > 1. In Java, the schema above is parsed without error, but when > attempting to use the default value, it fails with a > NullPointerException (trying to find the symbol C in E1). > I tried it with gogen-avro <https://github.com/actgardner/gogen-avro> and I had a similar issue. It generates invalid Go code as output. 2. If you were to disambiguate the symbols using the Avro JSON > encoding ("default": [{"E1":"B"},{"E2":"A"},{"E2":"C"}]), Java fails > while parsing the schema: > > org.apache.avro.AvroTypeException: Invalid default for field F: > [{"E1":"B"},{"E2":"A"},{"E2":"C"}] not a > > {"type":"array","items":[{"type":"enum","name":"E1","symbols":["A","B"]},{"type":"enum","name":"E2","symbols":["B","A","C"]}]} > at org.apache.avro.Schema.validateDefault(Schema.java:1542) > at org.apache.avro.Schema.access$500(Schema.java:87) > at org.apache.avro.Schema$Field.<init>(Schema.java:523) > at org.apache.avro.Schema.parse(Schema.java:1649) > at org.apache.avro.Schema$Parser.parse(Schema.java:1396) > at org.apache.avro.Schema$Parser.parse(Schema.java:1384) > > It seems that Java implements `Only the first schema in any union can > be used in a default value` as opposed to `Default values for union > fields correspond to the first schema in the union` (in the example, > it isn't a union field). > > Naively, I would expect any JSON encoded data to be a valid default > value (which is not what the spec says). Does anyone know why the > "first schema only" rule was added to the spec? > Yes, I think the authors missed a trick here. I suspect things would be cleaner if the default value was encoded in exactly the way as JSON-encoded Avro values. As things currently are, an implementer needs to implement two slightly different ways of translating from JSON to an Avro value. cheers, rog.
