[jira] [Commented] (BEAM-92) Data-dependent sinks

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEAM-92?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16081471#comment-16081471 ] 

ASF GitHub Bot commented on BEAM-92:
------------------------------------

Github user asfgit closed the pull request at:

    https://github.com/apache/beam/pull/3356


> Data-dependent sinks
> --------------------
>
>                 Key: BEAM-92
>                 URL: https://issues.apache.org/jira/browse/BEAM-92
>             Project: Beam
>          Issue Type: New Feature
>          Components: sdk-java-core
>            Reporter: Eugene Kirpichov
>            Assignee: Reuven Lax
>
> Current sink API writes all data to a single destination, but there are many use cases where different pieces of data need to be routed to different destinations where the set of destinations is data-dependent (so can't be implemented with a Partition transform).
> One internally discussed proposal was an API of the form:
> {code}
> PCollection<Void> PCollection<T>.apply(
>     Write.using(DoFn<T, SinkT> where,
>                 MapFn<SinkT, WriteOperation<WriteResultT, T>> how)
> {code}
> so an item T gets written to a destination (or multiple destinations) determined by "where"; and the writing strategy is determined by "how" that produces a WriteOperation (current API - global init/write/global finalize hooks) for any given destination.
> This API also has other benefits:
> * allows the SinkT to be computed dynamically (in "where"), rather than specified at pipeline construction time
> * removes the necessity for a Sink class entirely
> * is sequenceable w.r.t. downstream transforms (you can stick transforms onto the returned PCollection<Void>, while the current Write.to() returns a PDone)



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