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https://issues.apache.org/jira/browse/BEAM-6511?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17122132#comment-17122132
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Kenneth Knowles commented on BEAM-6511:
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This issue is assigned but has not received an update in 30 days so it has been
labeled "stale-assigned". If you are still working on the issue, please give an
update and remove the label. If you are no longer working on the issue, please
unassign so someone else may work on it. In 7 days the issue will be
automatically unassigned.
> AbstractGlobalCombineFn hierarchy is inconsistent
> -------------------------------------------------
>
> Key: BEAM-6511
> URL: https://issues.apache.org/jira/browse/BEAM-6511
> Project: Beam
> Issue Type: Bug
> Components: runner-dataflow
> Affects Versions: 2.9.0
> Reporter: Nahuel Lofeudo
> Assignee: Tyler Akidau
> Priority: P2
> Labels: stale-assigned
> Attachments: combineFn-hierarchy.png
>
>
> Subclasses of AbstractGlobalCombineFn seem to be arranged in a way that
> prevents them from being used with the DataflowRunner.
> Subclasses of AbstractGlobalCombineFn are under either CombineFn or
> CombineFnWithContext, which seems to be in itself a CombineFn which has
> access to PipelineOptions and Side Inputs.
> However, the DataflowRunner casts all combiners passed from user code to
> CombineFn (see [1]) which prevents combiners that extend CombineFnWithContext
> from being used there.
>
> For example:
> public class CustomCombinerFn extends
> CombineWithContext.CombineFnWithContext<...> \{...}
>
> final PCollectionView<SomeObject<String>> newCollection = oldCollection
> .apply("Custom Combiner", Combine.globally(new CustomCombinerFn(filter))
> .withSideInputs(filter)
> .withoutDefaults()
> .asSingletonView());
>
> IMHO either CombineFnWithContext should be a subclass of CombineFn or
> DataflowRunner should cast the combiner to AbstractGlobalCombineFn.
>
> [1]
> https://github.com/apache/beam/blob/b83b302ef97767e4ca245ea24e8bd40a6692e72c/runners/google-cloud-dataflow-java/src/main/java/org/apache/beam/runners/dataflow/DataflowRunner.java#L514
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