On Tue, Sep 19, 2006 at 09:51:23AM -0400, [EMAIL PROTECTED] wrote: > On Tue, Sep 19, 2006 at 08:20:13AM -0500, Jim C. Nasby wrote: > > On Mon, Sep 18, 2006 at 07:45:07PM -0400, [EMAIL PROTECTED] 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. > > It does, as I control the MAC address. I can choose not to overwrite it. > I can choose to ensure that any cases where it is overwritten, it is > overwritten with a unique value. Random number does not provide this > level of control. > > > 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. > > Which standard UUID generation function would you be thinking of? > Inventing a new one doesn't seem sensible. I'll have to read over the > versions again...
I don't think it exists, but I don't see how that's an issue. Let's look at an extreme case: take the amount of random entropy used for the random-only generation method. Append that to the current time in UTC, and hash it. Thanks to the time component, you've now greatly reduced the odds of a duplicate, probably by many orders of magnitude. Ultimately, I'm OK with a generator that's only in contrib, provided that there's at least one that will work on all OSes. -- Jim Nasby [EMAIL PROTECTED] EnterpriseDB http://enterprisedb.com 512.569.9461 (cell) ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings