| From: | Peter Geoghegan <pg(at)heroku(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com>, 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: | 2013-10-22 00:22:01 |
| Message-ID: | CAM3SWZTeeL+Rch9-UObftmJowu6rd8fO7B=zzqRbwsjxHPVi1A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Oct 21, 2013 at 4:29 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Hm. It's been a long time since college statistics, but doesn't the
> entire concept of standard deviation depend on the assumption that the
> underlying distribution is more-or-less normal (Gaussian)?
I don't see how. The standard deviation here would be expressed in
units of milliseconds. Now, that could be misleading, in that like a
mean average, it might "mischaracterize" the distribution. But it's
still got to be a big improvement.
I like the idea of a decay, but can't think of a principled scheme offhand.
--
Peter Geoghegan
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