Hi! This is an excellent question; don't have time to reply in much detail
right now, but please take a look at http://s.apache.org/splittable-do-fn -
it unifies the concepts of bounded and unbounded sources, and the use case
you mentioned is one of the motivating examples.
Also, see recent discus
Hello,
A use case I find myself running into frequently is the following: I have daily
or hourly files, and a Beam pipeline with a small to moderate size windows.
(Actually, I've just seen that support for per-window files support in file
based sinks was recently checked in, which is one way to
