From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mitch Skinner <mitch@egcrc.net>
Cc: pgsql-performance@postgresql.org
Subject: Re: same plan, add 1 condition, 1900x slower
Date: Fri, 11 Nov 2005 09:09:36 -0500
Message-ID: <18036.1131718176@sss.pgh.pa.us> (raw)
In-Reply-To: <1131700635.29496.136.camel@enzian>
References: <1131630176.29496.91.camel@enzian>
<10164.1131643400@sss.pgh.pa.us>
<1131700635.29496.136.camel@enzian>
Mitch Skinner <mitch@egcrc.net> writes:
> On Thu, 2005-11-10 at 12:23 -0500, Tom Lane wrote:
>> Apparently, you are using a platform and/or locale in which strcoll() is
>> spectacularly, god-awfully slow --- on the order of 10 msec per comparison.
> The version with the condition is definitely doing more I/O. The
> version without the condition doesn't read at all.
That's pretty interesting, but what file(s) is it reading exactly?
It could still be strcoll's fault. The only plausible explanation
I can think of for strcoll being so slow is if for some reason it were
re-reading the locale definition file every time, instead of setting up
just once.
If it is hitting Postgres files, it'd be interesting to look at exactly
which files and what the distribution of seek offsets is.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, mitch@egcrc.net
Subject: Re: same plan, add 1 condition, 1900x slower
In-Reply-To: <18036.1131718176@sss.pgh.pa.us>
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