From: | "Alexander Staubo" <alex(at)purefiction(dot)net> |
---|---|
To: | "Jeff Davis" <pgsql(at)j-davis(dot)com> |
Cc: | "gonzales(at)linuxlouis(dot)net" <gonzales(at)linuxlouis(dot)net>, "Guillaume Lelarge" <guillaume(at)lelarge(dot)info>, "Kenneth Downs" <ken(at)secdat(dot)com>, nikolay(at)samokhvalov(dot)com, pgsql-general(at)postgresql(dot)org |
Subject: | Re: Slightly OT. |
Date: | 2007-06-01 18:57:36 |
Message-ID: | 88daf38c0706011157y144dfc4m79dd745ae3a60198@mail.gmail.com |
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Lists: | pgsql-general |
On 6/1/07, Jeff Davis <pgsql(at)j-davis(dot)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.
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