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Re: Few questions on postgresql (dblink, 2pc, clustering)

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: jimworke(at)inbox(dot)lv
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Few questions on postgresql (dblink, 2pc, clustering)
Date: 2004-08-22 03:02:05
Message-ID: 200408220302.i7M325P15367@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-general
Jim Worke wrote:
> Hi list,
> 
> My boss would like to convert from MySQL to PostgreSQL, but there are a few 
> things that hold us back.
> 
> We'd like to have the databases in several physical servers, with referential 
> integrity between the tables.  Reading from Oracle articles, their 
> referential integrity can be done using their dblink and triggers.  What I'd 
> like to ask is whether contrib/dblink is stable?  Seeing dblink in a contrib 

It is certainly stable, but it does not have transaction semantics like
local table queries.

> directory does bring a doubt (though we've read many success stories with 
> dblink).  And can the Oracle's way of doing referential integrity be used in 
> PostgreSQL?  Is it recommended to do that?

Again, no persistent locking.,

> I've read the PostgreSQL's TODO list, and I can't find anything about 2-phase 
> commit being implemented in 8.0.  Is this correct?  Because I also read 
> there's a 2PC patch being implemented (http://snaga.org/pgsql/).  But 
> progress seems to have stopped (correct me if I'm wrong).

2-phase isn't in 8.0 but I expect it in 8.1.

> Basically, our concern is that dblink, 2PC implementation are there, but not 
> in the PostgreSQL mainstream.

You need to understand the limitations of dblink and see if it will work
for you.  I can't imagine MySQl is allowing you to do this cleanly so I
don't see why it would hold up a MySQL -> PostgreSQL migration.

> Another thing that bothers us is that we can't find any multi-master 
> clustering solution in PostgreSQL.  We're actually evaluating MySQL's own 
> clustering solution, but it's production quality release is still slated for 
> MySQL 5.0.

The only multi-master I know of is pgcluster.  There is talking of
moving Slony from master/slave to multi-master but work has not started
yet.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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