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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Commented] (BEAM-1198) ViewFn: explicitly decouple runner materialization of side inputs from SDK-specific mapping
Date Wed, 21 Dec 2016 22:41:58 GMT


ASF GitHub Bot commented on BEAM-1198:

GitHub user kennknowles opened a pull request:

    [BEAM-1198, BEAM-846, BEAM-260] Refactor Dataflow translator to decouple input and output
graphs more easily

    Be sure to do all of the following to help us incorporate your contribution
    quickly and easily:
     - [x] Make sure the PR title is formatted like:
       `[BEAM-<Jira issue #>] Description of pull request`
     - [ ] Make sure tests pass via `mvn clean verify`. (Even better, enable
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     - [x] Replace `<Jira issue #>` in the title with the actual Jira issue
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     - [x] If this contribution is large, please file an Apache
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    This is preparatory work to make it possible for the translator to have a more loosely
coupled relationship between its input and output.

You can merge this pull request into a Git repository by running:

    $ git pull Dataflow-Translator

Alternatively you can review and apply these changes as the patch at:

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #1678
commit 8ed4bb68660c537e4a12c1077ecfa104f9a82eaa
Author: Kenneth Knowles <>
Date:   2016-12-21T22:21:50Z

    Inline needless interface DataflowTranslator.TranslationContext
    The only implementation was DataflowTranslator.Translator. This class
    needs some updating and the extra layer of the interface simply
    obscures that work.

commit 272d06d7507ad7162616dd1b613efa7c8f5f4069
Author: Kenneth Knowles <>
Date:   2016-12-21T22:34:27Z

    Explicitly pass Step to mutate in Dataflow translator
    Previously, there was always a "current" step that was the most recent
    step created. This makes it cumbersome or impossible to do things like
    translate one primitive transform into a small subgraph of steps. Thus
    we added hacks like CreatePCollectionView which are not actually part
    of the model at all - in fact, we should be able to add the needed
    CollectionToSingleton steps simply by looking at the side inputs of a
    ParDo node.


> ViewFn: explicitly decouple runner materialization of side inputs from SDK-specific mapping
> -------------------------------------------------------------------------------------------
>                 Key: BEAM-1198
>                 URL:
>             Project: Beam
>          Issue Type: New Feature
>          Components: beam-model-fn-api, beam-model-runner-api
>            Reporter: Kenneth Knowles
>            Assignee: Kenneth Knowles
> For side inputs, the field {{PCollectionView.fromIterableInternal}} implies an "iterable"
materialization of the contents of a PCollection, which is adapted to the desired user-facing
type within a UDF (today the PCollectionView "is" the UDF)
> In practice, runners get adequate performance by special casing just a couple of types
of PCollectionView in a rather cumbersome manner.
> The design to improve this is and this
makes the de facto standard approach the actual model.

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