>> I have not tested this code, but it should work. You know how it is with code you don't test... alas ;-) I commented on the issue and uploaded a new patch that uses the union. I suspect the instanceOf check in GenericDatumWriter#resolveUnion is faulty, but I may just not understand the framework well enough.
> It should also work to add new schemas to the list as you write the file, > before adding records of each type. How would that work? Create a new writer (and discard the old one) based on the union but reuse the output stream? Cheers, Elco
