Re: Storing images in PostgreSQL databases (again)

you could store the pkey as a md5 or sha1 of the image's data. or any
of the other large hashing algorithms. that way your index only has to
compare 32 or 40 bytes instead of kilobytes per row.

as for the main color, you could generate histogram-like columns (or
even a single column) with the relative strengths of each channel and
store them into a smallint or bitstring. you could then do whatever you
wanted per channel and it could be indexed.

________________________________

From: pgsql-general-owner(at)postgresql(dot)org
[mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Jean-Christophe
Roux
Sent: Thursday, October 05, 2006 7:55 PM
To: Alexander Staubo
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: [GENERAL] Storing images in PostgreSQL databases (again)

Why would I set a bytea column (containing picures) as a primary key?
Because I want to be sure that the same image is inserted only once
(that requirement comes from a real project) and using a primary key for
that purpose makes sense to me.
Am I going to retrieve an image row by its image data? I would certainly
like! For instance, I would like to get the pictures whose main color is
green (requirement from a real project), and a
select * from images where main_color(image) = 'green' would be nice.
JCR

----- Original Message ----
From: Alexander Staubo <alex(at)purefiction(dot)net>
To: Jean-Christophe Roux <jcxxr(at)yahoo(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Sent: Thursday, October 5, 2006 7:35:04 PM
Subject: Re: [GENERAL] Storing images in PostgreSQL databases (again)

On Oct 6, 2006, at 01:29 , Jean-Christophe Roux wrote:

> By the way, is it practical to set a bytea column (containing
> pictures) as primary key? That would severely slow down many
> operations I guess.

Why would you? It's possible, but completely impractical, since image
data typically exceeds the index page size. Moreover, are you really
going to retrieve an image row by its image data?

Alexander.

---------------------------(end of broadcast)---------------------------
TIP 1: if posting/reading through Usenet, please send an appropriate
subscribe-nomail command to majordomo(at)postgresql(dot)org so that your
message can get through to the mailing list cleanly