Subject: Re: why vacuum
From: Mario Splivalo <mario.splivalo@mobart.hr>
Reply-To: mario.splivalo@mobart.hr
To: Andrew Sullivan <ajs@crankycanuck.ca>
Cc: pgsql-sql@postgresql.org
In-Reply-To: <20051027102120.GA26612@phlogiston.dyndns.org>
References: <200510261015.17623.lawgon@thenilgiris.com>
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Organization: Mob-Art
Date: Thu, 27 Oct 2005 14:34:13 +0200
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On Thu, 2005-10-27 at 06:21 -0400, Andrew Sullivan wrote:
> On Thu, Oct 27, 2005 at 10:22:41AM +0200, Mario Splivalo wrote:
> > offers no replication at all, you need to use slony (wich is also a poor
> > replacement for a wannabe replication), or some other commercial
> > products. What about 2PC? What about linking the databases from
> 
> Slony is in fact a community-supported system; so I don't know why
> you think that amounts to "no replication at all".  And since this is
> a community-supported system, it'd be nice if you said why it's a
> "poor replacement for wannabe replication".  What's wrong with it?

Postgres itself offers no replication. You could achive some sort of
replication by restoring the parts of WAL files, but that's rather
inconvinient. Then, if you want to replicate your data in any way, you
need to take slony, or whatever is existant out there, commercial or
open-free-source.
I appologize here if I insulted the slony developers, I ment nothing
like that :) I am sorry. I was just addressing the issue where
replication to one means 'just move my data here', and at others it
means 'merge my data'.

> > Btw, I 'ported' the merge replication from MSSQL to postgres. It
> > basicaly adds triggers to every table that is 'published' for
> > replication. There is a separate table to store and calculate the change
> > differences from several servers (so you could do update on any of the
> > servers and change will be propagated to the others). I'm missing 2PC
> > badly here, I wrote some stupid python 'thingie' wich should act as 2PC
> > serializer, but that's slow as hell. And triggers slow down postgres
> > quite a bit.
> 
> This is interesting.  Care to package it up for others, or write a
> proof-of-concept outline for the lists or General Bits or something
> like that?  This is a different sort of replication people are asking
> for.  Note that you get 2PC in the next Postgres release.

I'll be glad to, I'm just not that familiar (in fact, i'm not familiar
at all) with the 'proof-of-cocept' or 'General Bits' terms, so if you
could http-redirect me, I'll be  most thankfull.

Mentioning the 2PC, is it available in pg8.1beta4?

	Mike
-- 
Mario Splivalo
Mob-Art
mario.splivalo@mobart.hr

"I can do it quick, I can do it cheap, I can do it well. Pick any two."