You should look at the Log Shipping option with Slony I:
http://www.slony.info/documentation/logshipping.html

It is perfect for situations where your subscriber is "untrusted" or
for using over slower WAN links, etc. I am not a Log Shipping expert,
but I just setup a log shipping subscriber and it is working very
well.

Some caveats are that you need at least one normal subscriber because
a normal subscriber is what creates the log shipping files. As I
understand, if you only have one master and you want one log shipping
subscriber, you'd have to setup a third node just to be a trusted
subscriber so it can create the log shipping files. This is fine for
me because I have a master and a trusted subscriber then I have a
third node replicating using log shipping. My reasons for using log
shipping were #1) a slower WAN link is involved, and #2) I do not want
this 3rd node to have any impact on the main node and the main
subscriber. That is, if replication communication breaks on the 3rd
node, I don't want that keeping #1 and #2 from replicating.

Important note: at least one other maillist user and I have found that
the slony_logshipper program that comes with Slony simply does not
work reliably. We have not had any response from the developer(s)
regarding it. Thus, we (he) developed our own shell scripts to do the
job. If you get to a point where you want to try log shipping
replication, I can send you a copy of the 2 shell scripts--one moves
the files over and the other applies them to your subscriber node.

The documentation for log shipping is a bit sparse. It took me about 2
days of tinkering and testing (in between putting other fires out) to
get it working. Now that it is working, it seems to be a good,
reliable solution. I do wonder why every SYNC event is replicated via
log shipping, but admittedly I don't understand all the features of
log shipping either. Whether you have any changes to replicate or not,
log shipping files are being constantly produced--thousands per day.
Without knowing better, I think I'd rather just have files created
when there are changes to apply.

Enjoy!

> Date: Sat, 5 Jul 2008 10:38:14 +0000
> From: Ehl Le <ehl22_12 at live.com>
> Subject: [Slony1-general] (no subject)
>
> All I want is that slony replicates one database on the slave, nothing more. That login-information stored in the slave's slony-database also contains the password to the master-server.  I just can't use trust on the master-server for auth, since as I said, there are also other users on the slave which could connect to the master without supplying a password then.
>
>
> Regards,
> ehl22
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