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From "Gabriel Reid (JIRA)" <>
Subject [jira] [Commented] (CRUNCH-437) Fix Crunch Spark duplicate value aggregation
Date Sun, 06 Jul 2014 18:51:34 GMT


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,

> Fix Crunch Spark duplicate value aggregation
> --------------------------------------------
>                 Key: CRUNCH-437
>                 URL:
>             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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