There are Beam schema providers that use Java reflection to get fields for classes with fields and auto-value classes. It isn't relevant for POJOs with "creators", because function arguments are ordered. We cache instances of schema coders, but there is no guarantee that it's deterministic between JVMs. As a result, I've seen cases when the construction of pipeline graphs and output schema is non-deterministic. It's especially relevant when writing data to external storage, where row schema becomes a table schema. There is a workaround to apply a transform that would make schema deterministic, for instance, by ordering fields by name.
I would see a benefit in making schemas deterministic by default or at least introducing a way to do so without writing custom code. What are your thoughts?
