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