Re: standard interfaces for replication providers

Ühel kenal päeval, K, 2006-08-09 kell 13:56, kirjutas Jim C. Nasby:
> On Wed, Aug 09, 2006 at 07:33:35AM +0000, Markus Schiltknecht wrote:
> > Hello Alfranio,
> >
> > alfranio correia junior wrote:
> > >Of course not...
> > >It is impossible to build a replication system entirely by only using
> > >triggers...
> >
> > Hm, I don't think it's impossible, just unpractical. Anyway, if you say
> > so yourself, I really doubt the use of GAPI. If you need to create your
> > own hooks anyway beside GAPI, why use GAPI at all? Better have one kind
> > of 'hooking' (i.e. with a dynamically loaded library).
>
> Why reinvent the wheel for everything if there was an interface that
> offered some of the needed functionality? Maybe PostgreSQL-R is simply
> too deep in the database for any of this to be useful, but I'm 99%
> certain that Slony could make use of some of this stuff, such as a hook
> on tuples being written out.

Slonys problems ar *not* in getting access to tuples written out. Why
fix something that aint broken ?

> Likewise, if there were hooks for WAL
> records and a way to inject WAL info into a backend it probably wouldn't
> be too hard to build WAL-based replication on top of that. Heck, PITR
> could probably be refactored to use such hooks.

What would it buy us ?

> One of the great things about Oracle is that they expose a hell of a lot
> of the technology they use to build features like replication; ie: take
> a look at DBMS_*.

Being an OSS project, postgresql exposes *everything* it has ;)

BTW, do you know how I can get something equivalent to postgresqls
snapshot from oracle ?

I know one case when people had to do a really lot of unefficient work
to find out which transactions had committed during an interval in
oracle.

> > >But definitely, there is a set of common requirements among a variety of
> > >replication systems. Moreover, such requirements are also useful to
> > >other systems as well.
> >
> > So far, they are only partly usable for replication. I never looked into
> > materialized views or anything else that would benefit from such triggers.
> >
> > Regards
> >
> > Markus
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 2: Don't 'kill -9' the postmaster
> >
>
--
----------------
Hannu Krosing
Database Architect
Skype Technologies OÜ
Akadeemia tee 21 F, Tallinn, 12618, Estonia

Skype me: callto:hkrosing
Get Skype for free: http://www.skype.com