We have bunch of servers running the app and rebuilding postgres with support for ossp_uuid on all servers is time consuming. Is there a way of doing it without third party dependency like ossp_uuid? Should I just run md5(random number), will itbe the same ?. According to description it seems that all uuid_generate_v4() does is simply generate md5 of random number. Thanks. On Fri, Jan 29, 2010 at 8:31 PM, Adrian von Bidder <avbidder@xxxxxxxxxxx> wrote: > > Hi, > > On Friday 29 January 2010 09.20:33 Joe Kramer wrote: >> I need to generate unique id which is not guessable unlike >> serial(integer) type. I need an id in format like md5 hash of random >> number. >> On top of that I need this id to be unique across multiple tables. > > Have a look at http://www.postgresql.org/docs/8.3/static/uuid-ossp.html > > The usual approach is that (given a sensible random generator[1]) uuid are > assumed to be unique[2]. So you don't need to check because the probability > of collisions is so small that for practical purposes you can just ignore > it. > > (If your engineer's mind balks at this, consider that you're trusting this > already when you use digital cryptography / signatures, for example https > certificates.) > > I haven't looked at this module myself, but from the experience with > generating gpg keys on an appliance: if you need lots of randomness, the > geneation of random numbers might be your bottleneck. OTOH, our platform > didn't have disks and usually there was no network traffic while your > average db server has both, and on many systems there is a hardware random > generator, so this might not be an issue. > > cheers > -- vbi > > > [1] like, for example: http://www.dilbert.com/strips/comic/2001-10-25/ > [2] you'll want v4 uuids > -- > Linus has opinions, I have opinions, everybody else has opinions, and > the only consistency here is that most of us are wrong most of the time. > -- Andrew Morton, OLS 2004 > -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
