Re: Autonomous Transaction (WIP)

On 2014-04-08 16:13:21 -0400, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > I'm also pretty unconvinced that multiple PGPROCs is the right way to
> > go. First, PGPROCs have a bunch of state in them that is assumed to
> > exist once per backend. We might find pretty substantial code churn
> > there if we try to go change that. Second, why do other backends
> > really need to know about our ATs? As far as I can see, if other
> > backends see the AT as a subtransaction of our top-level transaction
> > up until it actually commits, that ought to be just fine.
>
> If we can make it work like that, sure. I'm a bit worried about how you'd
> decouple a subtransaction and commit it atomically ... or if that's not
> atomic, will it create any problems? The point being that you need to
> change both pg_subtrans and pg_clog to make that state transition.

I think it can be made work sensibly - while those states are changed it
will still appear to be running via the procarray. There's some fun
around suboverflowed entries, but I think that can be handled by
reserving an entry for autonomous transactions.

Greetings,

Andres Freund

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