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https://issues.apache.org/jira/browse/BEAM-490?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Luke Cwik updated BEAM-490:
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Fix Version/s: First stable release
> Swap to using CoGBK as grouping primitive instead of GBK
> --------------------------------------------------------
>
> Key: BEAM-490
> URL: https://issues.apache.org/jira/browse/BEAM-490
> Project: Beam
> Issue Type: Improvement
> Components: beam-model-fn-api, beam-model-runner-api, runner-core
> Reporter: Luke Cwik
> Labels: backwards-incompatible
> Fix For: First stable release
>
>
> The intent is for the semantics of both GBK and CoGBK to be
> unchanged, just swapping their status as primitives.
> 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
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