Re: GUID for postgreSQL

Magnus Hagander wrote:

>>
>
>At least on Windows, the GUID is derived in part from the computers
>primary MAC address. No, it's not a guarantee, but it's pretty unlikely
>:-)
>
>
The danger is not that the MAC address will be duplicated, but that
other factors will lead to an MD5 collision.

Unless you can show me that there is a 1:1 correspondence of all
possible unique factors going into the GUID generation and the output,
then I will say it is still no guarantee.

Just because two documents or files have the same MD5 doesn't mean that
they are the same files either. I.e. you can't go searching all files
by MD5 checksums and expecting to find the right one. OTOH, MD5
provides reasonable assurance that any given file (once you know its
intended MD5) has not been tampered with. I.e. MD5 is not meant to
preclude collisions, but rather it is meant to preclude *intentional*
collisions. Similarly, if we want a guaranteed uniqueness to a GUID we
have to have some sort of unique string to the GUID prepended to it (not
merely used in a hash).

So you could use the Mac address of the machine, I guess, if you wanted
to....

Best Wishes,
Chris Travers
Metatron Technology Consulting