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Re: [PERFORM] Help with tuning this query (with explain analyze finally)

From: "Dave Held" <dave(dot)held(at)arrayservicesgrp(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,"John A Meinel" <john(at)arbash-meinel(dot)com>
Cc: "Magnus Hagander" <mha(at)sollentuna(dot)net>,"Ken Egervari" <ken(at)upfactor(dot)com>,<pgsql-performance(at)postgresql(dot)org>,<pgsql-hackers-win32(at)postgresql(dot)org>
Subject: Re: [PERFORM] Help with tuning this query (with explain analyze finally)
Date: 2005-03-07 22:34:32
Message-ID: 49E94D0CFCD4DB43AFBA928DDD20C8F90261846B@asg002.asg.local (view raw or flat)
Thread:
Lists: pgsql-hackers-win32pgsql-performance
> -----Original Message-----
> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
> Sent: Monday, March 07, 2005 10:39 AM
> To: John A Meinel
> Cc: Magnus Hagander; Ken Egervari; pgsql-performance(at)postgresql(dot)org;
> pgsql-hackers-win32(at)postgresql(dot)org
> Subject: Re: [pgsql-hackers-win32] [PERFORM] Help with tuning 
> this query
> (with explain analyze finally)
> 
> [...]
> The EXPLAIN ANALYZE instrumentation code will really be happier with a
> straight time-since-bootup counter; by using gettimeofday, it is
> vulnerable to giving wrong answers if someone changes the date setting
> while the EXPLAIN is running.  But there is (AFAIK) no such call among
> the portable Unix syscalls.  It seems reasonable to me to #ifdef that
> code to make use of QueryPerformanceCounter on Windows.  This does not
> mean we want to alter the behavior of gettimeofday() where it's being
> used to find out the time of day.

There is always clock().  It's mandated by ANSI C, but my docs say
that POSIX requires CLOCKS_PER_SEC == 1000000 regardless of actual
timer resolution, which seems a little brain-dead to me.

__
David B. Held
Software Engineer/Array Services Group
200 14th Ave. East,  Sartell, MN 56377
320.534.3637 320.253.7800 800.752.8129

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