I need to join from a superclass attribute to its subclass entity (they are using JOINED inheritance). Tried something like this:
In the end I got it working by constructing the query the other way round - so instead of attempting to join to a subclass it was simply using the parent metamodel class:
This worked for my use case but expect there may still be situations where the question needs a better answer - e.g. where the required set of joins includes both children and parents.