why not have server a start at 1 and server b start at max int8/2. that will give each server alot of orders before you have an issue. They will will not have to play games with the sequence value. Jim ---------- Original Message ----------- From: Philippe Ferreira <phil.f@xxxxxxxxxxxxxx> To: Martijn van Oosterhout <kleptog@xxxxxxxxx> Cc: jim@xxxxxxxxxxxxxx, pgsql-general@xxxxxxxxxxxxxx Sent: Sat, 28 Jan 2006 17:46:55 +0100 Subject: Re: [GENERAL] My very first PL/pgSQL procedure... > >I think you need to provide a rationale why you want to control the > >value of the sequence in such a way anyway, because you're trying to do > >something that the system isn't likely to support. The numbers are > >supposed to be "opaque", the actual values are not supposed to be > >relevent. > > > >Have a nice day, > > > > > Hi, > > Actually, I'm building a switchover/failover system (based on WAL) for > my own needs. > > There is no problem for the switchover, because the data is properly > synched during > this procedure. > > However, when I have to start the failover on a secondary server, some > changes can > be "uncommited" at the time of the failover. > So, as soon as the primary PostgreSQL server is up again, I have to resync > (automatically or manually) these "uncommited" changes to the failover > node, before > switching properly to the primary. > > Actually, I've got a sequence which generates order numbers. These codes > will be > always unique, even in case of failover, since I alter the definition of the > sequence depending on the server (primary or secondary), with a suffix > of 'A' or 'B'. > For example, imagine the following scenario : > > ------------------------------------------------ > > Server A : Server B : > ========== ========== > 1000A > 1001A > 1002A > ---[SWITCHOVER]--> > 1003B > 1004B > 1005B > 1006B > <--[SWITCHOVER]--- > 1007A > 1008A > 1009A > 1010A [FAILOVER]--> 1010B > 1011A 1011B > 1012A - > 1013A - > [RESYNC]--> 1010A > [RESYNC]--> 1011A > [RESYNC]--> 1012A > [RESYNC]--> 1013A > <--[SWITCHOVER]--- > 1014A > 1015A > > ------------------------------------------------ > > So, in this example, if I don't increment the last value of my > sequence from 1011 to 1013 (before my last "SWITCHOVER"), it > will output "1012A" (instead of 1014A), and my new record will > conflict with an existing one !! > > Thank you for your interest, > Philippe Ferreira. > > ---------------------------(end of broadcast)--------------------------- > TIP 9: In versions below 8.0, the planner will ignore your desire to > choose an index scan if your joining column's datatypes do not > match ------- End of Original Message -------
