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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Commented] (BEAM-1234) Consider a hint ParDo.withHighFanout()
Date Tue, 18 Jul 2017 17:32:00 GMT


ASF GitHub Bot commented on BEAM-1234:

GitHub user sb2nov opened a pull request:

    Change PR template from 1234 to XXX

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    @jkff PTAL

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    This closes #3587
commit b827f65622f9cd9203803b76935aac422c179803
Author: Sourabh Bajaj <>
Date:   2017-07-18T17:30:44Z

    Change PR template from 1234 to XXX


> Consider a hint ParDo.withHighFanout()
> --------------------------------------
>                 Key: BEAM-1234
>                 URL:
>             Project: Beam
>          Issue Type: Improvement
>          Components: sdk-java-core
>            Reporter: Eugene Kirpichov
>            Priority: Minor
> I'm finding myself again and again suggesting users on StackOverflow to insert fusion
breaks after high-fanout ParDo's.
> I think we should just implement this as a hint on ParDo and MapElements transforms,
like we have on GroupByKey.fewKeys() or Combine.withHotKeyFanout().
> E.g.: c.apply(ParDo.of(some high-fanout DoFn).withHighFanout()), and a runner that implements
fusion could decide to insert a runner-specific fusion break. This somewhat sidesteps the
issues in and
because every runner can decide how to do the right thing, or is free to ignore the hint.

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