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From ChengXiangLi <...@git.apache.org>
Subject [GitHub] flink pull request: [FLINK-2549] add topK operator to DataSet.
Date Tue, 22 Sep 2015 09:04:44 GMT
GitHub user ChengXiangLi opened a pull request:

    https://github.com/apache/flink/pull/1161

    [FLINK-2549] add topK operator to DataSet.

    The topK operator is implemented with `mapPartition()` followed by `reduceGroup()`, each
map tasks select top k elements, and transfer to singleton reduce task(no `group()` before
`reduceGroup()`), and then select top k elements in reduce task. 
    The main part of this implementation:
    1. An out-of-core self managed memory based PriorityQueue implementation.
    2.  Use runtime resources to build PriorityQueue for UDF. topK is not real 'native' operator
actually, it contains UDF which use self managed memory based PriorityQueue to select top
k elements.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/ChengXiangLi/flink priorityqueue

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/flink/pull/1161.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #1161
    
----
commit 7165d5ba78376cec1b3c752afb949e6273d45869
Author: chengxiang li <chengxiang.li@intel.com>
Date:   2015-09-16T02:10:05Z

    [FLINK-2549] add topK operator to DataSet.

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