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https://issues.apache.org/jira/browse/BEAM-9748?focusedWorklogId=422801&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-422801
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ASF GitHub Bot logged work on BEAM-9748:
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Author: ASF GitHub Bot
Created on: 15/Apr/20 15:56
Start Date: 15/Apr/20 15:56
Worklog Time Spent: 10m
Work Description: lukecwik commented on issue #11406: [BEAM-9748] Move
Reparallelize transform to Reshuffle
URL: https://github.com/apache/beam/pull/11406#issuecomment-614121831
> The comments inside Reparallelize explain how this transform differs from
Reshuffle.viaRandomKey(): it performs dramatically better on Dataflow in case
the input PCollection is generated highly sequentially, as in the case of
reading several GB of JDBC results. It almost certainly performs somewhat worse
if the input PCollection is generated in a well-parallelized way, but I haven't
measured that; I haven't measured the former case for non-Dataflow runners
either.
>
> I think it's reasonable to move this to Reshuffle, but rename it to
something more clear: maybe Reshuffle.forSequentiallyGeneratedInput()?
I see. You would imagine that two materializations once because of the side
input fusion break and then the reshuffle would be more expensive overall.
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Issue Time Tracking
-------------------
Worklog Id: (was: 422801)
Time Spent: 2h 20m (was: 2h 10m)
> Add Reshuffle.ForSequentiallyGeneratedInput transform
> -----------------------------------------------------
>
> Key: BEAM-9748
> URL: https://issues.apache.org/jira/browse/BEAM-9748
> Project: Beam
> Issue Type: Improvement
> Components: sdk-java-core
> Reporter: Ismaël Mejía
> Assignee: Ismaël Mejía
> Priority: Minor
> Time Spent: 2h 20m
> Remaining Estimate: 0h
>
> Some DoFn based IOs like JdbcIO and RedisIO rely on a different approach to
> Reparallelize outputs using a combination of a an empty PCollectionView to
> force materialization and Reshuffle.viaRandomkey to reparallelize a
> PCollection. This issue extracts this transform and expose it as part of the
> Reshuffle to avoid repeating the code for transforms (notably IOs) that
> produce lots of sequentially generated data where and benefit of this
> alternative approach to perform better reparallelization of its output.
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