I asked on user a while ago and didn't get an answer, so I'm wondering if anyone has an idea if this would be hard to add in a PR:
Given a DoFn<B,C> and PCollection<KV<A,B>> can we make it so we can get back a PCollection<KV<A<C>>? Is there a way to make it generic so it works for PCollection<T<A,B>>? The use cases are numerous. Instead of using side inputs in a streaming pipeline, we can enrich some data with readAll from various sources. Itt would make a lot of sense to be able to reuse those readAll transforms instead of writing a custom DoFn to grab data from Redis, Sql, etc. This also seems fairly compostable as well so you could continue to enrich data with multiple sources. *~Vincent*
