[jira] [Resolved] (SPARK-7041) Avoid writing empty files in BypassMergeSortShuffleWriter

["Sean Owen (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-7041?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sean Owen resolved SPARK-7041.
------------------------------
          Resolution: Duplicate
    Target Version/s:   (was: 1.6.0)

I'll close this in favor of the more recent issue since there is an active PR and discussion there.

> Avoid writing empty files in BypassMergeSortShuffleWriter
> ---------------------------------------------------------
>
>                 Key: SPARK-7041
>                 URL: https://issues.apache.org/jira/browse/SPARK-7041
>             Project: Spark
>          Issue Type: Improvement
>          Components: Shuffle
>            Reporter: Josh Rosen
>            Assignee: Josh Rosen
>
> In BypassMergeSortShuffleWriter, we may end up opening disk writers files for empty partitions; this occurs because we manually call {{open()}} after creating the writer, causing serialization and compression input streams to be created; these streams may write headers to the output stream, resulting in non-zero-length files being created for partitions that contain no records.  This is unnecessary, though, since the disk object writer will automatically open itself when the first write is performed.  Removing this eager {{open()}} call and rewriting the consumers to cope with the non-existence of empty files results in a large performance benefit for certain sparse workloads when using sort-based shuffle.



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