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Posted to issues@beam.apache.org by "ASF GitHub Bot (JIRA)" <ji...@apache.org> on 2019/04/01 20:02:00 UTC

[jira] [Work logged] (BEAM-6906) Mutating accumulators in fused stages is generally unsafe - need to provide a single mutable accumulator

     [ https://issues.apache.org/jira/browse/BEAM-6906?focusedWorklogId=221449&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-221449 ]

ASF GitHub Bot logged work on BEAM-6906:
----------------------------------------

                Author: ASF GitHub Bot
            Created on: 01/Apr/19 20:01
            Start Date: 01/Apr/19 20:01
    Worklog Time Spent: 10m 
      Work Description: robinyqiu commented on issue #8134: [BEAM-6906] Update spec on CombineFn and DoFn to clarify mutability of parameters
URL: https://github.com/apache/beam/pull/8134#issuecomment-478724935
 
 
   Ping @kennknowles 
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 221449)
    Time Spent: 0.5h  (was: 20m)

> Mutating accumulators in fused stages is generally unsafe - need to provide a single mutable accumulator
> --------------------------------------------------------------------------------------------------------
>
>                 Key: BEAM-6906
>                 URL: https://issues.apache.org/jira/browse/BEAM-6906
>             Project: Beam
>          Issue Type: Bug
>          Components: beam-model
>            Reporter: Kenneth Knowles
>            Assignee: Yueyang Qiu
>            Priority: Critical
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> Our current docs encourage a CombineFn author to mutate accumulators for efficiency. This is important, but cannot be done generally without losing efficiency - it is not safe to share accumulators within a stage or across sliding windows. The ownership story needs to be clear. Any accumulator that is mutable is from that point on owned by the CombineFn, not the runner and cannot be given to other steps.



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