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From scwf <>
Subject [GitHub] spark pull request: [SPARK-8968] [SQL] shuffled by the partition c...
Date Fri, 10 Jul 2015 05:15:52 GMT
Github user scwf commented on the pull request:
    >This patch we shuffle data by the partition columns firstly so that each partition
will have ony one partition file and this also reduce the gc overhead.
    @liancheng here i am not mean the partition of spark rdd, i mean for each partition for
the table such as `.../a=2/b=5` there will be only one file. before this where maybe many
small files under the partition dir.
    @cloud-fan @liancheng I have tested this patch and it shows that the performance not become
bad(in my situation, it improved 20%-30%).
    Anyway i will also have a try to use ExternalSorter to do a local sorting  and will report
the performance later.

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