[jira] [Commented] (CRUNCH-437) Fix Crunch Spark duplicate value aggregation

["Gabriel Reid (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CRUNCH-437?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14053180#comment-14053180 ] 

Gabriel Reid commented on CRUNCH-437:
-------------------------------------

I'm a bit late on this, but for future reference, another way of doing this would have been replacing the HashMultimap with an ArrayListMultimap (which has the semantics of Map<K, List<V>>)

> Fix Crunch Spark duplicate value aggregation
> --------------------------------------------
>
>                 Key: CRUNCH-437
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-437
>             Project: Crunch
>          Issue Type: Bug
>            Reporter: Josh Wills
>             Fix For: 0.8.4, 0.11.0
>
>         Attachments: CRUNCH-437.patch
>
>
> The current Crunch-on-Spark mapside combiner uses a Multimap of key-value pairs to cache values for local aggregation. This is awesome, except it means that identical key-value outputs before a shuffle will only have one copy in the Multimap, which means that the aggregation counts may not be correct. We should fix it to use a proper Map<K, List<V>> to ensure that duplicate values are aggregated correctly.



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