Re: GUID for postgreSQL

chris(at)travelamericas(dot)com (Chris Travers) writes:
>>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.

What factors?

The 'random' portion comes _in addition to_ location information and a
timestamp, so that for there to be a collision, you need to be
generating thousands of GUIDs *per millisecond* on a given host.

> 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.

Read the RFC (4122). It shows how it works.

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

That is one option; section 4.3 of the RFC suggests an alternative
that is also likely to work.
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