Alexander Staubo wrote:
On 6/1/07, Jeff Davis <pgsql@xxxxxxxxxxx> 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.
As the owner of a company that actually actively developing a
replication system and has for years... I suggest you start putting your
code where your words are.
This is not nearly as simple as it seems. There is a reason that Slony
attempts to do it in user space instead of postgresql space.
Joshua D. Drake
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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