Re: dbmirror revisions

From: nolan(at)celery(dot)tssi(dot)com
To: pgsql-general(at)postgresql(dot)org (pgsql list)
Subject: Re: dbmirror revisions
Date: 2003-04-05 17:38:20
Message-ID: 20030405173820.1416.qmail@celery.tssi.com
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I am probably out of my depth here as this seems to be getting into the
internals of the pgsql replication project. I'm not part of that project,
and I've only been using pgsql for a few months, though I have nearly
10 years of experience with Oracle, including master/slave replication.
(In retrospect, this is probably a thread I should not have jumped into.)

> Why do you think that would be better? It is already done in a perl
> function that launches SQL ...
>
> > If there are INDEPENDENT sequences on the master and the slave, what's to
> > guarantee uniqueness?
>
> Not sure I understand the question. Uniqueness in what respect?

Correct me if I'm wrong, but isn't the primary goal of a sequence to
ensure uniqueness of the sequence values?

It's atomic and non-transactional (ie, sequences cannot be rolled back),
and in a data replication environment there must be some method of ensuring
that the sequence remains atomic, which is to say that there is really
only ONE sequence that is shared among the replication nodes.
--
Mike Nolan

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