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https://issues.apache.org/jira/browse/BEAM-440?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kenneth Knowles updated BEAM-440:
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Assignee: Jason White
> 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
> Assignee: Jason White
> 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}}:
> {code}
> 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());
> {code}
> 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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