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https://issues.apache.org/jira/browse/BEAM-115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15344778#comment-15344778
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ASF GitHub Bot commented on BEAM-115:
-------------------------------------
GitHub user kennknowles opened a pull request:
https://github.com/apache/incubator-beam/pull/520
[BEAM-115] Add ViewFn to SDK and adjust PCollectionView impls
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---
This is a small adjustment that reflects the language-independent
architecture in the Java code, leaving the prior structure in place temporarily
for ease of migration.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/kennknowles/incubator-beam ViewFn
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-beam/pull/520.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #520
----
commit 56204137e4dbaaf1ea30770fb7927f27fa777805
Author: Kenneth Knowles <k...@google.com>
Date: 2016-06-22T15:39:33Z
Add ViewFn to SDK and adjust PCollectionView impls
----
> Beam Runner API
> ---------------
>
> Key: BEAM-115
> URL: https://issues.apache.org/jira/browse/BEAM-115
> Project: Beam
> Issue Type: Improvement
> Components: runner-core
> Reporter: Kenneth Knowles
> Assignee: Kenneth Knowles
>
> The PipelineRunner API from the SDK is not ideal for the Beam technical
> vision.
> It has technical limitations:
> - The user's DAG (even including library expansions) is never explicitly
> represented, so it cannot be analyzed except incrementally, and cannot
> necessarily be reconstructed (for example, to display it!).
> - The flattened DAG of just primitive transforms isn't well-suited for
> display or transform override.
> - The TransformHierarchy isn't well-suited for optimizations.
> - The user must realistically pre-commit to a runner, and its configuration
> (batch vs streaming) prior to graph construction, since the runner will be
> modifying the graph as it is built.
> - It is fairly language- and SDK-specific.
> It has usability issues (these are not from intuition, but derived from
> actual cases of failure to use according to the design)
> - The interleaving of apply() methods in PTransform/Pipeline/PipelineRunner
> is confusing.
> - The TransformHierarchy, accessible only via visitor traversals, is
> cumbersome.
> - The staging of construction-time vs run-time is not always obvious.
> These are just examples. This ticket tracks designing, coming to consensus,
> and building an API that more simply and directly supports the technical
> vision.
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