Re: [HACKERS] Replication documentation addition

Markus Schiltknecht wrote:
> Good morning Bruce,
>
> Bruce Momjian wrote:
> >> Oops, I see Markus Schiltknech likes the term "statement-based
> >> replication" better too. Certainly master-slave communication using
> >> "statement-based replication" has the same drawbacks as the broadcast
> >> method, but I wanted to highlight that the broadcast was happening
> >> outside the server. Do we need a master/slave "statement-based
> >> replication" item and a middleware broadcast item?
>
> Ah, I see you had a much narrower definition of statement-based
> replication in mind. As I've pointed out, there are different
> implementations of 'statement-based replication'. I don't know about
> sequoia, but Postgres-R fails back to statement based replication in
> certain situations. Thus having an external 'program intercept every SQL
> query' is absolutely no necessity of this algorithm, it can very well be
> done inside the db backend, where you can better catch non-deterministic
> functions... but again, that's an implementation detail.
>
> So, do you want to describe pgpool here or do you want to give a more
> general description?

OK, I have updated the title to be "Statement-Based Replication Using
Middleware". I personally think statement-based replication only makes
sense in middleware because when you are in the backend, you have more
information and can do things better, either by modifying the statement
or passing actual data rows, like Slony does, so I want to restrict this
to middleware like pgpool, and Usogres, which was an early
implementation of this idea.

> > <varlistentry>
> > <term>Statement-Based Replication</term>
> > <listitem>
> >
> > <para>
> > In statement-based replication, a program intercepts every SQL
> > query and sends it to all servers. Each server operates
> > independently. Read-only queries can be sent to a single server
> > because there is no need for all servers to process it.
> > </para>
>
> If you want to go for the general description, I think the 'each server
> operates independently' is somewhere between confusing and false. And
> again, the last sentence applies to all multi-master replication solutions.

Am I OK now?

--
Bruce Momjian bruce(at)momjian(dot)us
EnterpriseDB http://www.enterprisedb.com

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