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https://issues.apache.org/jira/browse/BEAM-12?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Frances Perry updated BEAM-12:
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Assignee: Frances Perry
Priority: Trivial (was: Major)
Component/s: sdk-java-core
If you need to do something to the elements to extract the key before grouping,
you can use a ParDo (or a derivative like MapElements). So something like:
input.apply(ParDo.of(new ExtractFn()))
.apply(GroupByKey.<K, V>create());
I'm not sure what you meant by automatically extracting keys from data -- that
sounds like something that would application or domain specific.
As always, if you find yourself using a pattern often in your applications, you
can create your own composite PTransform do it more compactly.
> Apply GroupByKey transforms on PCollection of normal type other than KV
> -----------------------------------------------------------------------
>
> Key: BEAM-12
> URL: https://issues.apache.org/jira/browse/BEAM-12
> Project: Beam
> Issue Type: Improvement
> Components: sdk-java-core
> Reporter: bakeypan
> Assignee: Frances Perry
> Priority: Trivial
>
> Now the GroupByKey transforms can only apply on PCollection<KV<K,V>>.So I
> have to transform PCollection<T> to PCollection<KV<K,V>> before I want to
> apply GroupByKey.
> I think we can do better by apply GroupByKey on normal type of PCollection
> other than KV.And user can offer one custome extract key function or we can
> offer default extract key function.Just like this:
> PCollection<T> input = ...
> PCollection<KV<K,Iterable<V>>> result = input.apply(GroupByKey.<K,
> V>create(new ExtractFn()));
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