Windows uses the MAC address in GUID generation. > -----Original Message----- > From: pgsql-general-owner@xxxxxxxxxxxxxx [mailto:pgsql-general- > owner@xxxxxxxxxxxxxx] On Behalf Of Scott Marlowe > Sent: Wednesday, July 27, 2005 1:47 PM > To: John DeSoi > Cc: Tino Wildenhain; Riaan van der Westhuizen; Postgresql-General > Subject: Re: GUID for postgreSQL > > On Wed, 2005-07-27 at 15:32, John DeSoi wrote: > > On Jul 27, 2005, at 4:49 AM, Tino Wildenhain wrote: > > > > > I'd create a sequence: > > > > > > CREATE SEQUENCE global_unique_id_seq; > > > > > > and a function: > > > > > > CREATE OR REPLACE FUNCTION newid() > > > RETURNS text AS > > > $BODY$ SELECT nextval('global_unique_id_seq')::text; $BODY$ > > > LANGUAGE 'sql' VOLATILE; > > > > > > > > > now every call to newid() returns a garantied unique id for > > > say the next 18446744073709551616 calls. > > > Of course you can obfuscate the ID even more using > > > md5, include servername and so on, but this will not improve > > > security in any way (unless you mix data with 2nd database) > > > > > > This is not really a viable replacement for a GUID == globally unique > > identifier. Here global means that if I use the application in > > multiple databases, I'm guaranteed that no two identifiers will be > > the same. Using a sequence will only support uniqueness for a single > > database. > > So, how can two databases, not currently talking to one another, > guarantee that their GUIDs don't collide? using a large randomly > generated name space only reduces the chances of collision, it doesn't > actually guarantee it. > > ---------------------------(end of broadcast)--------------------------- > TIP 3: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faq ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
