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On 10/05/06 18:54, Jean-Christophe Roux wrote:
> 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.
A hash function makes better sense. SHA-1 creates a 20 byte string
that is the digest of the file. Almost perfect as a primary key.
SHA-256 (so far!) guarantees uniqueness in 32 bytes.
> 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.
That would speedily be handled by preprocessing metadata records as
the image is inserted.
- --
Ron Johnson, Jr.
Jefferson LA USA
Is "common sense" really valid?
For example, it is "common sense" to white-power racists that
whites are superior to blacks, and that those with brown skins
are mud people.
However, that "common sense" is obviously wrong.
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