GitHub user ggevay opened a pull request:
https://github.com/apache/flink/pull/910
[FLINK-2148] [contrib] Exact and approximate countDistinct on streams
For the approximate calculation I used the HyperLogLog implementation in
the Clearspring library.
Currently it operates only on the entire stream, but when the dust settles
around the windowing rewrite, I will modify this code to work on windows
instead. The Clearspring implementation has a merge method, which means that it
is compatible with windowing aggregation optimizations like panes or B-Int.
I have also added a fromArray convenience method to
StreamExecutionEnvironment.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/ggevay/flink countDistinct
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/910.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 #910
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commit f0ae6a06daec7a016f756f9db436b2e1e56a3c46
Author: Gabor Gevay <gga...@gmail.com>
Date: 2015-07-13T19:59:10Z
[FLINK-2148] [contrib] Exact and approximate countDistinct on streams
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