+1 I assume that the intent is for the semantics of both GBK and CoGBK to be unchanged, just swapping their status as primitives.
This seems like a good change, with strictly positive impact on users and SDK authors, with only an extremely minor burden (doing an insertion of the provided implementation in the worst case) on runner authors. Kenn On Wed, Jul 20, 2016 at 10:38 AM, Lukasz Cwik <lc...@google.com.invalid> wrote: > I would like to propose a change to Beam to make CoGBK the basis for > grouping instead of GBK. The idea behind this proposal is that CoGBK is a > more powerful operator then GBK allowing for two key benefits: > > 1) SDKs are simplified: transforming a CoGBK into a GBK is trivial while > the reverse is not. > 2) It will be easier for runners to provide more efficient implementations > of CoGBK as they will be responsible for the logic which takes their own > internal grouping implementation and maps it onto a CoGBK. > > This requires the following modifications to the Beam code base: > > 1) Make GBK a composite transform in terms of CoGBK. > 2) Move the CoGBK from contrib to runners-core as an adapter*. Runners that > more naturally support GBK can just use this and everything executes > exactly as before. > > *just like GroupByKeyViaGroupByKeyOnly and UnboundedReadFromBoundedSource >
