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https://issues.apache.org/jira/browse/BEAM-6511?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Beam JIRA Bot updated BEAM-6511:
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Labels: (was: stale-P2)
> 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
> Priority: P3
> 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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