Hi Team, I'm currently thinking about how we can bring the broadcast set/broadcast input feature form the DataSet API to the DataStream API. I think this would be a valuable addition since it would enable use cases that join streams with constant (or slowly changing) side information.
For this purpose, I think that we need to change the way we handle stream operators. The new model would have one unified operator that handles all cases and allows to add inputs after the operator was constructed, thus allowing the specification of broadcast inputs. I wrote up this preliminary document detailing the reason why we need such a new operator for broadcast inputs and also what the API of such an operator would be. It also quickly touches on the required changes of existing per-operation stream operations such as StreamMap: https://docs.google.com/document/d/1ZFzL_0xGuUEnBsFyEiHwWcmCcjhd9ArWsmhrgnt05RI/edit?usp=sharing Please have a look if you're interested. Feedback/insights are very welcome. :-) Cheers, Aljoscha
