Github user scwf commented on the pull request:
https://github.com/apache/spark/pull/7336#issuecomment-120229996
>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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