Re: Transactions involving multiple postgres foreign servers, take 2

At Tue, 20 Oct 2020 02:44:09 +0000, "tsunakawa(dot)takay(at)fujitsu(dot)com" <tsunakawa(dot)takay(at)fujitsu(dot)com> wrote in
> From: Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
> > Using pg_cancel_backend() and pg_terminate_backend() a DBA can cancel
> > running query from any backend or terminate a backend. For either to
> > work the backend needs to be interruptible. IIRC, Robert had made an
> > effort to make postgres_fdw interruptible few years back.
>
> Yeah, I know those functions. Sawada-san was talking about Ctrl + C, so I responded accordingly.
>
> Also, how can the DBA find sessions to run those functions against? Can he tell if a session is connected to or running SQL to a given foreign server? Can he terminate or cancel all session with one SQL command that are stuck in accessing a particular foreign server?

I don't think the inability to cancel all session at once cannot be a
reason not to not to allow operators to cancel a stuck session.

> Furthermore, FDW is not cancellable in general. So, I don't see a point in trying hard to make only commit be cancelable.

I think that it is quite important that operators can cancel any
process that has been stuck for a long time. Furthermore, postgres_fdw
is more likely to be stuck since network is involved so the usefulness
of that feature would be higher.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center