| From: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
|---|---|
| To: | Peter Geoghegan <pg(at)heroku(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Gavin Flower <GavinFlower(at)archidevsys(dot)co(dot)nz>, KONDO Mitsumasa <kondo(dot)mitsumasa(at)lab(dot)ntt(dot)co(dot)jp>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Add min and max execute statement time in pg_stat_statement |
| Date: | 2013-10-21 22:48:52 |
| Message-ID: | 5265AF54.1000207@dunslane.net |
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| Lists: | pgsql-hackers |
On 10/21/2013 04:43 PM, Peter Geoghegan wrote:
> On Mon, Oct 21, 2013 at 1:36 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> Yeah, and I worry about min and max not being very usable - once they
>> get pushed out to extreme values, there's nothing to drag them back
>> toward normality except resetting the stats, and that's not something
>> we want to encourage people to do frequently.
> My thoughts exactly. Perhaps it'd be useful to separately invalidate
> min/max times, without a full reset. But then you've introduced the
> possibility of the average time (total_time/calls) exceeding the max
> or being less than the min.
>
>
This is why I suggested the standard deviation, and why I find it would
be more useful than just min and max. A couple of outliers will set the
min and max to
possibly extreme values but hardly perturb the standard deviation over a
large number of observations.
cheers
andrew
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