| From: | Arne Scheffer <arne(dot)scheffer(at)uni-muenster(dot)de> |
|---|---|
| To: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, KONDO Mitsumasa <kondo(dot)mitsumasa(at)lab(dot)ntt(dot)co(dot)jp>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Rajeev rastogi <rajeev(dot)rastogi(at)huawei(dot)com>, Mitsumasa KONDO <kondo(dot)mitsumasa(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Subject: | Re: Add min and max execute statement time in pg_stat_statement |
| Date: | 2015-01-20 18:26:07 |
| Message-ID: | permail-201501201826078954262000006bbe-scheffa@message-id.uni-muenster.de |
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| Lists: | pgsql-hackers |
Interesting patch.
I did a quick review looking only into the patch file.
The "sum of variances" variable contains
the "sum of squared differences" instead, I think.
And a very minor aspect:
The term "standard deviation" in your code stands for
(corrected) sample standard deviation, I think,
because you devide by n-1 instead of n to keep the
estimator unbiased.
How about mentioning the prefix "sample"
to indicate this beiing the estimator?
And I'm sure I'm missing C specifics (again)
(or it's the reduced patch file scope),
but you introduce sqrtd, but sqrt is called?
VlG
Arne
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