Re: Proof of concept: standalone backend with full FE/BE protocol - Mailing list pgsql-hackers

On 13 November 2012 17:38, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:
>> The most popular relational database in the world is Microsoft Access,
>> not MySQL. Access appears desirable because it allows a single user to
>> create and use a database (which is very good). But all business
>> databases have a requirement for at least one of: high availability,
>> multi-user access or downstream processing in other parts of the
>> business.
>
> That's a mighty sweeping claim, which you haven't offered adequate
> evidence for.  The fact of the matter is that there is *lots* of demand
> for simple single-user databases, and what I'm proposing is at least a
> first step towards getting there.

I agree there is lots of demand for simple single-user databases and I
wish that too. What I don't agree with is something that casts that
requirement in stone by architecturally/permanently disallowing
secondary connections.

Evidence for claims:
* The whole Business Intelligence industry relies on being able to
re-purpose existing data, forming integrated webs of interconnecting
databases. All of that happens after the initial developers write the
first version of the database application.
* Everybody wants a remote backup, whether its for your mobile phone
contact list or your enterprise datastore.

People are migrating away from embedded databases in droves for these
very reasons.

> The main disadvantage of approaching this via the existing single-user
> mode is that you won't have any autovacuum, bgwriter, etc, support.
> But the flip side is that that lack of infrastructure is a positive
> advantage for certain admittedly narrow use-cases, such as disaster
> recovery and pg_upgrade.  So while I agree that this isn't the only
> form of single-user mode that we'd like to support, I think it is *a*
> form we'd like to support, and I don't see why you appear to be against
> having it at all.

I have no problem with people turning things off, I reject the idea
that we should encourage people to never be able to turn them back on.

> A more reasonable objection would be that we need to make sure that this
> isn't foreclosing the option of having a multi-process environment with
> a single user connection.  I don't see that it is, but it might be wise
> to sketch exactly how that case would work before accepting this.

Whatever we provide will become the norm. I don't have a problem with
you providing BOTH the proposed single user mode AND the multi-process
single user connection mode in this release. But if you provide just
one of them and its the wrong one, we will be severely hampered in the
future.

Yes, I am very much against this project producing a new DBMS
architecture that works on top of PostgreSQL data files, yet prevents
maintenance, backup, replication and multi-user modes.

I see this decision as a critical point for this project, so please
consider this objection and where it comes from.

-- Simon Riggs                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services