Re: max_standby_delay considered harmful

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Mon, May 3, 2010 at 11:37 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I'm inclined to think that we should throw away all this logic and just
>> have the slave cancel competing queries if the replay process waits
>> more than max_standby_delay seconds to acquire a lock.

> What if we somehow get into a situation where the replay process is
> waiting for a lock over and over and over again, because it keeps
> killing conflicting processes but something restarts them and they
> take locks over again?

They won't be able to take locks "over again", because the lock manager
won't allow requests to pass a pending previous request, except in
very limited circumstances that shouldn't hold here. They'll queue
up behind the replay process's lock request, not in front of it.
(If that isn't the case, it needs to be fixed, quite independently
of this concern.)

regards, tom lane