[wp-hackers] Time to change GUID to UUID?

Lynne Pope lynne.pope at gmail.com
Mon May 9 00:18:08 UTC 2011

On Mon, May 9, 2011 at 2:38 AM, Eric Mann <eric at eam.me> wrote:

> Lynn, using your example the only real way to guarantee global uniqueness
> for the GUIDs would be to use some kind of external service that keeps
> track.  I say this, because even hashes can (theoretically) repeat for
> different content.
> Some suggestions I've seen for making GUIDs into real GUIDs (in this thread
> and in the past:
>   - Use the UUID feature of MySQL
>   - Hash the URL of the post
>   - Hash the URL of the post with a hash of the content
>   - Hash the URL of the post with the site name as a salt
> In isolation, none of these can be guaranteed as unique against other
> sites.
>  If we were to use one of any of them, we'd still potentially run into your
> problem of person B taking over an abandoned site and ending up with a GUID
> that duplicates a value used by the previous site owner.  True, it'd be a
>  rare case, but a real possibility.

The example I gave is what happens now. Basing the GUID on the domain name
is far from unique.
Creating a string from a salted URI + timestamp + cryptographic quality
highly-random number is far more likely to give practical uniqueness. UUID's
can never be absolutely unique across all of time and space but they can get
pretty close.


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