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https://issues.apache.org/jira/browse/SPARK-3533?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14711291#comment-14711291
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Jason Hubbard commented on SPARK-3533:
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Spark SQL has the ability to write to multiple file locations already
SPARK-3007. I'm not recommending converting your RDD to DataFrame just to
write to multiple locations, but it might be beneficial for them to share the
same mechanism. One current limitation of the Spark SQL implementation is that
each split will open a new Writer for each hive partition, and if there are a
lot of hive partitions spread across the splits then it will cause many small
files and possibly degrade performance because of memory usage.
> Add saveAsTextFileByKey() method to RDDs
> ----------------------------------------
>
> Key: SPARK-3533
> URL: https://issues.apache.org/jira/browse/SPARK-3533
> Project: Spark
> Issue Type: Improvement
> Components: PySpark, Spark Core
> Affects Versions: 1.1.0
> Reporter: Nicholas Chammas
>
> Users often have a single RDD of key-value pairs that they want to save to
> multiple locations based on the keys.
> For example, say I have an RDD like this:
> {code}
> >>> a = sc.parallelize(['Nick', 'Nancy', 'Bob', 'Ben',
> >>> 'Frankie']).keyBy(lambda x: x[0])
> >>> a.collect()
> [('N', 'Nick'), ('N', 'Nancy'), ('B', 'Bob'), ('B', 'Ben'), ('F', 'Frankie')]
> >>> a.keys().distinct().collect()
> ['B', 'F', 'N']
> {code}
> Now I want to write the RDD out to different paths depending on the keys, so
> that I have one output directory per distinct key. Each output directory
> could potentially have multiple {{part-}} files, one per RDD partition.
> So the output would look something like:
> {code}
> /path/prefix/B [/part-1, /part-2, etc]
> /path/prefix/F [/part-1, /part-2, etc]
> /path/prefix/N [/part-1, /part-2, etc]
> {code}
> Though it may be possible to do this with some combination of
> {{saveAsNewAPIHadoopFile()}}, {{saveAsHadoopFile()}}, and the
> {{MultipleTextOutputFormat}} output format class, it isn't straightforward.
> It's not clear if it's even possible at all in PySpark.
> Please add a {{saveAsTextFileByKey()}} method or something similar to RDDs
> that makes it easy to save RDDs out to multiple locations at once.
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