Re: help optimise this ?

"Peter Galbavy" <peter(dot)galbavy(at)knowtion(dot)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