Unfortunately, stateful transdcuers like Unique cannot be used after parallelizable transdcuer like ReducePartitonBy. It’s kind of a cost of parallelizability. There can be a better design to allow this but it’s a bit tricky to do ATM.
I think it would be useful to be able to compose these transducers, so I'm requesting that feature here.
@tkf wrote
I think it would be useful to be able to compose these transducers, so I'm requesting that feature here.