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https://issues.apache.org/jira/browse/CRUNCH-213?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gabriel Reid updated CRUNCH-213:
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Attachment: CRUNCH-213.patch
Patch to introduce sharded joins. The join code is also pretty thoroughly
refactored, introducing the concept of a JoinStrategy, with three
implementations: DefaultJoinStrategy, MapsideJoinStrategy, and
ShardedJoinStrategy.
> Add sharded join functionality
> ------------------------------
>
> Key: CRUNCH-213
> URL: https://issues.apache.org/jira/browse/CRUNCH-213
> Project: Crunch
> Issue Type: New Feature
> Reporter: Gabriel Reid
> Assignee: Gabriel Reid
> Attachments: CRUNCH-213.patch
>
>
> Performing joins where a large proportion of the values on one or both sides
> of the join are mapped to a single key can result in poor performance, as one
> (or a small number) of reducers end up handling most of the joining work,
> leaving the rest of the cluster idle.
> Sharded joining should be added to allow splitting up join keys, thereby
> distributing values mapped to a single key over multiple reducer partitions.
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