[Pgpool-general] Replication Flawed?

[Jim C. Nasby]

On Wed, May 17, 2006 at 09:55:25AM -0400, Andrew Sullivan wrote:
> On Wed, May 17, 2006 at 03:02:25PM +0200, Robert Ayres wrote:
> 
> > I have run the same tests (and passed) using a JDBC based
> > replication system, Sequoia (sequoia.continuent.org), which ensures
> > replication consistency by ordering statements from all
> > transactions based on ids assigned to them AFAIK.
> 
> Sequoia can't guarantee replication either.  Try doing SELECT now()
> on two machines, down to the millisecond.  I bet you get very
> slightly different answers.  Or better, select oid from pg_class
> where tname = [something]. 

Actually, Continuent's replication solution will look for things like
now() in commands and replace it with an actual timestamp, so they've
made some efforts to mitigate the problems with statement-based
replication. But there's still plenty of issues, which is why I
generally don't care for it.

As for OID's in pg_class, the only 'replication' scheme that protects
against that is PITR.
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby at pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461