[PROPOSAL] KeyedPCollection design draft

[Jan Lukavský <je...@seznam.cz>]

Hi,

as a follow-up from a discussion [1] about reiterations over result from 
a GBK I have put together a very basic draft of a design document [2] 
which could be a solution to the problem (and maybe several others).

I'd be vary happy to hear about what do people think about the basic 
outlines of proposed solution and the possibilities it might open. 
Please don't take the draft as a complete proposal, there are still some 
open questions and considerations that should be made, for now I'd like 
to find out how the community would generally feel about the proposed 
changes. I didn't want to dig too far into the details, but hopefully 
the intention should be clear.

Looking forward to comments! :)

  Jan


[1] 
https://lists.apache.org/thread.html/5e71c98a32bcbc536f55f91f3e81e90ab7384c6ea56bdb30a92fcb31@%3Cdev.beam.apache.org%3E

[2] 
https://docs.google.com/document/d/1fdAz-IvFQ3xxYOGskByo_9lI82iQlAtPvZHZb-h3z20/edit?usp=sharing