[jira] [Work logged] (BEAM-4030) Add CombineFn.compact, similar to Java

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BEAM-4030?focusedWorklogId=180841&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-180841 ]

ASF GitHub Bot logged work on BEAM-4030:
----------------------------------------

                Author: ASF GitHub Bot
            Created on: 03/Jan/19 19:30
            Start Date: 03/Jan/19 19:30
    Worklog Time Spent: 10m 
      Work Description: aaltay commented on issue #7405: [BEAM-4030] Add compact attribute to combiners
URL: https://github.com/apache/beam/pull/7405#issuecomment-451251480
 
 
   cc: @katsiapis
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 180841)
    Time Spent: 20m  (was: 10m)

> Add CombineFn.compact, similar to Java
> --------------------------------------
>
>                 Key: BEAM-4030
>                 URL: https://issues.apache.org/jira/browse/BEAM-4030
>             Project: Beam
>          Issue Type: Bug
>          Components: sdk-py-core
>            Reporter: Robert Bradshaw
>            Assignee: Ahmet Altay
>            Priority: Major
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> Some CombineFns buffer elements in their add_inputs because a combining operation cost can be effectively amortized across many elements. However, this introduces the extra (possibly higher) cost of potentially serializing more expensive buffers through shuffle. We should add a CombineFn.compact(self, accumulator) method (defaulting to the identity) similar to what the Java SDK provides which is called when flushing an element from the PGBKCV table. 



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