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https://issues.apache.org/jira/browse/BEAM-440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15425458#comment-15425458
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ASF GitHub Bot commented on BEAM-440:
-------------------------------------
GitHub user JasonMWhite opened a pull request:
https://github.com/apache/incubator-beam/pull/843
[BEAM-440] add Create#empty
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---
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/JasonMWhite/incubator-beam create_empty
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-beam/pull/843.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 #843
----
commit d38b30204d1201b9146dd69bd312ec066314912d
Author: Jason White <[email protected]>
Date: 2016-08-16T23:35:47Z
add Create#empty
----
> Create.values() returns a type-unsafe Coder
> -------------------------------------------
>
> Key: BEAM-440
> URL: https://issues.apache.org/jira/browse/BEAM-440
> Project: Beam
> Issue Type: Bug
> Components: sdk-java-core
> Reporter: Daniel Halperin
> Labels: newbie, starter
>
> Create.values() with no arguments will default to a VoidCoder, unless one is
> set later with #setCoder(Coder).
> Although it will encode its input correctly, this seems like a bad choice in
> many cases. E.g., with Flatten:
> PCollection<KV<SomeClass, Integer>> initial = p.apply("First",
> Create.<KV<SomeClass, Integer>>of());
> PCollection<KV<SomeClass, Integer>> second =
> p.apply("Second", Create.of("a", "b")).apply(ParDo.of(new
> MyAvroDoFn()));
> PCollectionList
> .of(initial).and(second)
> .apply(Flatten.<KV<SomeClass, Integer>>pCollections());
> This crashes trying to cast a KV from "Second" to a Void.class.
> 1. Suggest throwing a warning in #getDefaultOutputCoder when defaulting to
> VoidCoder for an empty elements list. Should this be an error?
> 2. Suggest adding something like Create.empty(TypeDescriptor) to handle this
> case properly.
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