Re: Confused by 'timing' results

Kevin
The problem I am trying to solve is:
measure accurately both the database server time + network time when several
clients connect to the database from different geographic location.
All the clients hit the database simultaneously with a long script each of
insert/update/select queries.

I don't need aggregate numbers but the 2 components of the time taken for each
and every query to drive analysis. So need in some fashion:
Query1, DB Time, Total Time (or Network Time)
....
Query<n>, DB Time, Total Time (or Network Time)

From the query, I can relate to what client in what geographic location fired
that query and so have the full picture.

I initially thought combination of time + timing will give me this. Now I know
'timing' includes part of network time , so it is not just the database server
time.
On second try, by trying to log to log_directory/log_filename by
setting log_min_duration_statement=0, seems to be doing something weird. The
durations are very very high in the file and cannot be true. My theory is that
it is a single file being written by several concurrent queries and so they
might be all queuing up causing the time being registered in this log file to be
way high. (I might be wrong)
I could not believe the times being registered in the log file (several hundred
ms as opposed to the expected few tens of ms) and ran the test several times
over couple of days, still getting the same high numbers.
On setting log_min_duration_statement=-1, the performance comes back to the
normal acceptable performance (but I cannot measure the db time).

So really what I want to measure is the database time for several queries by
several concurrent users. Because each query takes only a few ms, any sort of
overhead has to be put carefully to not skew the measurement being tried.

Looking for suggestions to solve this.

Thank you, AJ

________________________________
From: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>; A J <s5aly(at)yahoo(dot)com>
Cc: pgsql-admin(at)postgresql(dot)org
Sent: Thu, September 2, 2010 12:48:58 PM
Subject: Re: [ADMIN] Confused by 'timing' results

A J <s5aly(at)yahoo(dot)com> wrote:
> I am conducting the test with several concurrent clients.

I didn't see a question in your latest email. Do you now understand
why the network affects timings? Do you have any other questions?
Is there some particular problem you're trying to solve, for which
you don't yet have a solution? (If so, please describe the problem
you're trying to solve; someone might be able to suggest a solution
you won't get to by asking narrower questions.)

-Kevin