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https://issues.apache.org/jira/browse/CRUNCH-213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13678660#comment-13678660
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Chao Shi commented on CRUNCH-213:
---------------------------------
Hi Gabriel,
I think the random sharding approach in PreShardRightSideFn is not
deterministic. This may result in unexpected behavior when speculative
execution is enabled. Given that numShards is generally small (am I right?), a
fixed random seed or simply round robin should be the same effective.
> 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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