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Re: [HACKERS] Patch for UUID datatype (beta)

From: "Jim C(dot) Nasby" <jimn(at)enterprisedb(dot)com>
To: mark(at)mark(dot)mielke(dot)cc
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org,Andreas Pflug <pgadmin(at)pse-consulting(dot)de>,Gevik Babakhani <pgdev(at)xs4all(dot)nl>,pgsql-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: [HACKERS] Patch for UUID datatype (beta)
Date: 2006-09-19 13:20:13
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Lists: pgsql-hackerspgsql-patches
On Mon, Sep 18, 2006 at 07:45:07PM -0400, mark(at)mark(dot)mielke(dot)cc wrote:
> I would not use a 100% random number generator for a UUID value as was
> suggested. I prefer inserting the MAC address and the time, to at
> least allow me to control if a collision is possible. This is not easy
> to do using a few lines of C code. I'd rather have a UUID type in core
> with no generation routine, than no UUID type in core because the code
> is too complicated to maintain, or not portable enough.

As others have mentioned, using MAC address doesn't remove the
possibility of a collision.

Maybe a good compromise that would allow a generator function to go into
the backend would be to combine the current time with a random number.
That will ensure that you won't get a dupe, so long as your clock never
runs backwards.
Jim Nasby                                    jimn(at)enterprisedb(dot)com
EnterpriseDB      512.569.9461 (cell)

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