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Posted to issues@spark.apache.org by "Sandy Ryza (JIRA)" <ji...@apache.org> on 2014/09/08 21:10:28 UTC
[jira] [Comment Edited] (SPARK-3441) Explain in docs that
repartitionAndSortWithinPartitions enacts Hadoop style shuffle
[ https://issues.apache.org/jira/browse/SPARK-3441?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14125936#comment-14125936 ]
Sandy Ryza edited comment on SPARK-3441 at 9/8/14 7:09 PM:
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Because we opted not to provide the grouping, the API isn't ideal for porting workloads from Hadoop - the amount of code required to replicate the Hadoop shuffle semantics is probably more than we can fit in the Javadoc. Not opposed to adding a note that it can be used as a building block.
I considered a version without a partitioner, but I couldn't think of a situation where one would care that records are sorted within a partition, but not need to be specific about what keys end up in what partitions. Anything you can think of that I'm missing?
was (Author: sandyr):
I'll add mention that this can be used to get Hadoop-style shuffle. Because we opted not to provide the grouping, the API isn't ideal for porting workloads from Hadoop - the amount of code required to replicate the Hadoop shuffle semantics is probably more than we can fit in the Javadoc. Not opposed to adding a note that it can be used as a building block.
I considered a version without a partitioner, but I couldn't think of a situation where one would care that records are sorted within a partition, but not need to be specific about what keys end up in what partitions. Anything you can think of that I'm missing?
> Explain in docs that repartitionAndSortWithinPartitions enacts Hadoop style shuffle
> -----------------------------------------------------------------------------------
>
> Key: SPARK-3441
> URL: https://issues.apache.org/jira/browse/SPARK-3441
> Project: Spark
> Issue Type: Improvement
> Components: Documentation, Spark Core
> Reporter: Patrick Wendell
> Assignee: Sandy Ryza
>
> I think it would be good to say something like this in the doc for repartitionAndSortWithinPartitions and add also maybe in the doc for groupBy:
> {code}
> This can be used to enact a "Hadoop Style" shuffle along with a call to mapPartitions, e.g.:
> rdd.repartitionAndSortWithinPartitions(part).mapPartitions(...)
> {code}
> It might also be nice to add a version that doesn't take a partitioner and/or to mention this in the groupBy javadoc. I guess it depends a bit whether we consider this to be an API we want people to use more widely or whether we just consider it a narrow stable API mostly for Hive-on-Spark. If we want people to consider this API when porting workloads from Hadoop, then it might be worth documenting better.
> What do you think [~rxin] and [~matei]?
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