From: Bruce Momjian <bruce@momjian.us>
Message-Id: <200611150011.kAF0Beb21787@momjian.us>
Subject: Re: [HACKERS] Replication documentation addition
In-Reply-To: 
 <Pine.LNX.4.64.0611141534330.23695@discord.home.frostconsultingllc.com>
To: Jeff Frost <jeff@frostconsultingllc.com>
Date: Tue, 14 Nov 2006 19:11:39 -0500 (EST)
CC: Chris Browne <cbbrowne@acm.org>, pgsql-docs@postgresql.org
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Jeff Frost wrote:
> On Tue, 14 Nov 2006, Bruce Momjian wrote:
> 
> >> My thinking on the definition of clustering was that there is some smarts for
> >> graceful failover and automated or semi-automated ways of bringing failed DB
> >> servers back up to date and online with the rest of the servers in the
> >> cluster.  All servers need to be able to accept writes, but do we
> >
> > No, even replication servers can have that.
> >
> >> differentiate on where the writes originated (i.e. middleware or another
> >> postgresql server) or on functionality?
> >
> > Fundamentally, broadcast means the queries are being propogated outside
> > the server, with the benefits and limitations inherent in that.
> 
> I'd definitely have to agree with you on that.  I guess I'm trying to decide 
> what differentiates clustering for load balancing from query broadcast based 
> on your text.  Maybe just don't use the word broadcast here:
> 
> "In clustering, each server can accept write requests, and these write 
> requests are broadcast from the original server to all other servers before 
> each transaction commits."
> 
> Unfortunately, I can't seem to come up with anything more clever.

Basically, when you are broadcasting outside the server, you are
broadcasting SQL queries, and those queries do not have information
about non-deterministic functions and have issues with universal commits
on all node.

I think I now see your point about using the word "broadcast" for both
clustering and middle-ware broadcast.  Let me find some new wording and
repost.

-- 
  Bruce Momjian   bruce@momjian.us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +