To: "Peter Galbavy" <peter.galbavy@knowtion.net>
Cc: pgsql-sql@postgresql.org
Subject: Re: help optimise this ? 
In-reply-to: <001d01c29169$79fd1d20$4528a8c0@cblan.mblox.com> 
References: <001d01c29169$79fd1d20$4528a8c0@cblan.mblox.com>
Comments: In-reply-to "Peter Galbavy" <peter.galbavy@knowtion.net>
	message dated "Thu, 21 Nov 2002 14:22:51 +0000"
Date: Thu, 21 Nov 2002 10:46:51 -0500
Message-ID: <12120.1037893611@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

"Peter Galbavy" <peter.galbavy@knowtion.net> writes:
> I want to then find either the largest (max) or smallest (min) version of an
> image that falls within some range of sizes:

Depends on how you want to define "largest" and "smallest", but if
"area" is a good enough definition, seems like this would work:

select file_md5 from image_instance
where md5 = '546b94e94851a56ee721f3b755f58462'
    and image_width between 0 and 160
    and image_length between 0 and 160
order by image_width * image_length
limit 1;

Probably an index on md5 would be sufficient to make this go fast ---
I assume you're not going to be storing a vast number of sizes of
the same image.

			regards, tom lane