[Pgpool-general] Pgpool and/or Slony

[Andrew Sullivan]

On Wed, Jan 17, 2007 at 04:12:52PM -0500, Brad Nicholson wrote:
> pgpool docs clearly state:
> 
> "Please note that certain queries are physically dependent to a server
> or non-deterministic. These include random functions, OID, XID, and
> timestamps may not be replicated in exactly same value among two
> servers. This is because query results for these are local to each
> PostgreSQL server."

Yes, but I'm pretty sure (I'm not looking at the docs now, and I'm
too lazy to test) that if you do

SELECT CURRENT_TIMESTAMP

or friends through pgpool (any flavour), it will catch and
re-interpret it.  The problem comes when you have, for instance, a
DEFAULT on a table that is CURRENT_TIMESTAMP.  Slony will handle this
correctly, but pgpool might cause the tables to drift.  I'm happy to
be corrected in the details; it makes no difference to your larger
point, which is certainly true.  There is no way in principle, for
instance, for a statement replicator to know that your stored
procedure calls another stored procedure that happens to call now(). 
It's always possible to cause statement-based replication to fail in
this way using _some_ method.  The question is mostly whether your
application trips over that limitation.  

A

-- 
Andrew Sullivan  | ajs at crankycanuck.ca
I remember when computers were frustrating because they *did* exactly what 
you told them to.  That actually seems sort of quaint now.
		--J.D. Baldwin