On 6/1/07, Jeff Davis <pgsql@j-davis.com> wrote:
> On Fri, 2007-06-01 at 17:00 +0200, Alexander Staubo wrote:
> > the projected Slony-II design, but the setup seems dead simple, and
> > from the docs I have found it seems to transparently replicate schema
> > changes, unlike Slony-I. So that's something.
>
> To be fair to Slony-I, the fact that it does not replicate DDL is a
> feature, not a bug. It's table-based, which is a very flexible design.
I fail to see how that's an excuse not to replicate DDL. If I run
"alter table" on the master, there is no reason whatever that this
command cannot be executed on all the slaves -- which is what I would
expect of a replication system.
To put it differently: A slave's table is a replica of the master's
table; if I alter the master table, and the slave is not updated to
reflect this change, then the slave table is no longer a true replica,
and the system has failed its core purpose, that of *replicating*.
I could be wrong, but I believe Slony fails at this because it is
trigger-based and simply cannot detect DDL changes.
Alexander.
