[jira] [Commented] (BEAM-2640) Introduce Create.ofProvider(ValueProvider)

["Eugene Kirpichov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEAM-2640?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16093588#comment-16093588 ] 

Eugene Kirpichov commented on BEAM-2640:
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Coder inference for this is complicated by the fact that ValueProvider does not expose a TypeDescriptor for the value being provided. Even though it could. I'm gonna start with requiring to explicitly provide a coder.

> Introduce Create.ofProvider(ValueProvider)
> ------------------------------------------
>
>                 Key: BEAM-2640
>                 URL: https://issues.apache.org/jira/browse/BEAM-2640
>             Project: Beam
>          Issue Type: New Feature
>          Components: sdk-java-core
>            Reporter: Eugene Kirpichov
>            Assignee: Eugene Kirpichov
>
> When you have a ValueProvider<T> that may or may not be accessible at construction time, a common task is to wrap it into a single-element PCollection<T>. This is especially common when migrating an IO connector that used something like Create.of(query) followed by a ParDo, to having query be a ValueProvider.
> Currently this is done in an icky way (e.g. https://github.com/apache/beam/blob/master/sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/datastore/DatastoreV1.java#L615)
> We should have a convenience helper for that.



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