From: Bruce Momjian <bruce@momjian.us>
Message-Id: <200611220404.kAM44mC22657@momjian.us>
Subject: Re: "Clustering"
In-Reply-To: <4563202E.3090403@bluegap.ch>
To: Markus Schiltknecht <markus@bluegap.ch>
Date: Tue, 21 Nov 2006 23:04:48 -0500 (EST)
CC: Peter Eisentraut <peter_e@gmx.net>, pgsql-docs@postgresql.org
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Markus Schiltknecht wrote:
> Hi,
> 
> I wrote:
> > That reminds me of the requirement of having Multi Master Replication in 
> > place to do Parallel Query Execution. Sync Multi Master Replication 
> > being better, while Async Multi Master Replication obviously leads to 
> > inconsistent responses, when queried in parallel. That may be acceptable 
> > in certain situations.
> 
> Oops, during rereading "Clustering For Parallel Query Execution", I've 
> noticed that you mention Data Partitioning as one possible way to do 
> Parallel Query Execution. Thus Multi Master Replication obviously is not 
> a requirement, but just another way to allow for Parallel Query 
> Execution. Mentioning that as well would probably be good.

Uh, multi-master replication allows for load balancing, but it doesn't
help a single query to run any faster.  Think of having only one query
running on the cluster.  Parallel execution allows a single query to use
more than one computer, right?

> IMHO, the advice to use multiple, independent databases to do parallel 
> query execution sounds a little meager. Of course it's also parallel 
> query execution, but it's not what most people suspect to find under 
> that section, I would guess.

Uh, this confuses me.  What is missing?  You split tables across
multiple servers.

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

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