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https://issues.apache.org/jira/browse/SPARK-5581?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15184491#comment-15184491
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Sital Kedia commented on SPARK-5581:
------------------------------------

Is anyone working on this issue? I would like to work on it, if not. We are 
seeing very bad map side performance when the number of partitions is too large 
because of this issue. 

> When writing sorted map output file, avoid open / close between each partition
> ------------------------------------------------------------------------------
>
>                 Key: SPARK-5581
>                 URL: https://issues.apache.org/jira/browse/SPARK-5581
>             Project: Spark
>          Issue Type: Improvement
>          Components: Shuffle
>    Affects Versions: 1.3.0
>            Reporter: Sandy Ryza
>
> {code}
>       // Bypassing merge-sort; get an iterator by partition and just write 
> everything directly.
>       for ((id, elements) <- this.partitionedIterator) {
>         if (elements.hasNext) {
>           val writer = blockManager.getDiskWriter(
>             blockId, outputFile, ser, fileBufferSize, 
> context.taskMetrics.shuffleWriteMetrics.get)
>           for (elem <- elements) {
>             writer.write(elem)
>           }
>           writer.commitAndClose()
>           val segment = writer.fileSegment()
>           lengths(id) = segment.length
>         }
>       }
> {code}



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