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https://issues.apache.org/jira/browse/BEAM-115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15965150#comment-15965150
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ASF GitHub Bot commented on BEAM-115:
-------------------------------------
GitHub user tgroh opened a pull request:
https://github.com/apache/beam/pull/2505
[BEAM-115] Represent a Pipeline via a list of Top-level Transforms
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---
The root node is a synthetic transform which does not appear within the
graph, as it never has any components of note. Instead of referring to a
single "root node" in the Pipeline message, refer to the top-level nodes
which do not have an enclosing PTransform.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/tgroh/beam top_level_transforms
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/beam/pull/2505.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 #2505
----
commit 31d5c272c4a6822ef35836be207224b557e122b4
Author: Thomas Groh <tg...@google.com>
Date: 2017-04-11T23:42:28Z
Represent a Pipeline via a list of Top-level Transforms
The root node is a synthetic transform which does not appear within the
graph, as it never has any components of note. Instead of referring to a
single "root node" in the Pipeline message, refer to the top-level nodes
which do not have an enclosing PTransform.
----
> Beam Runner API
> ---------------
>
> Key: BEAM-115
> URL: https://issues.apache.org/jira/browse/BEAM-115
> Project: Beam
> Issue Type: Improvement
> Components: beam-model-runner-api
> 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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