GitHub user sirpkt opened a pull request:
https://github.com/apache/tajo/pull/427
TAJO-921: Add STDDEV_SAMP and STDDEV_POP window functions
Implementing STDDEV_SAMP() and STDDEV_POP() as aggregation funciton.
- Calculation is based on the method first proposed by B. P. Welford in
1962 and described by Donald Knuth in Art of Computer Programming, Volume 2:
Seminumerical Algorithms.
(You can also check
http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Online_algorithm
for basic explanation)
- I also changes names of test methods for window functions (for example,
from rowNumber1 to testRowNumber1)
I checked 'mvn clean install' passed with this patch.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/sirpkt/tajo TAJO-921
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/tajo/pull/427.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 #427
----
commit e8f8ca78b30b8efb5eb8418b3d811a7053cd24f5
Author: Keuntae Park <[email protected]>
Date: 2015-03-17T01:58:58Z
Implement aggregation functions STDDEV_SAMP and STDDEV_POP
commit 406f3113c796d79c6f6888b68eac00a8ee0f5039
Author: Keuntae Park <[email protected]>
Date: 2015-03-17T04:54:09Z
Merge remote-tracking branch 'upstream/master' into TAJO-921
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