Re: Add progressive backoff to XactLockTableWait functions

Hi,

On Wed, Jul 2, 2025 at 10:56 PM Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>
wrote:

>
>
> On 2025/07/02 23:19, Andres Freund wrote:
> > Hi,
> >
> > On July 2, 2025 10:15:09 AM EDT, Fujii Masao <
> masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
> >>
> >>
> >> On 2025/07/02 23:04, Andres Freund wrote:
> >>> Hi,
> >>>
> >>> On 2025-07-02 22:55:16 +0900, Fujii Masao wrote:
> >>>> On 2025/06/24 1:32, Xuneng Zhou wrote:
> >>>>> 3. The proposed solution
> >>>>>
> >>>>> If the above analysis is sound, one potential fix would be to add
> >>>>> separate branching for standby in XactLockTableWait. However, this
> seems
> >>>>> inconsistent with the function's definition—there's simply no lock
> entry
> >>>>> in the lock table for waiting. We could implement a new function for
> >>>>> this logic,
> >>>>
> >>>> To be honest, I'm fine with v3, since it only increases the sleep time
> >>>> after 5000 loop iterations, which has negligible performance impact.
> >>>
> >>> I think this is completely the wrong direction. We should make
> >>> XactLockTableWait() on standbys, not make the polling smarter.
> >>
> >> On standby, XactLockTableWait() can enter a busy loop with 1ms sleeps.
> >
> > Right.
> >
> >> But are you suggesting that this doesn't need to be addressed?
> >
> > No.
> >
> >> Or do you have another idea for how to handle it?
> >
> > We have all the information to make it work properly on standby. I've
> not find through the code to figure out not, but that's what needs to
> happen, instead on putting on another layer of hacks.
>
> Sorry, maybe I failed to get your point...
> Could you explain your idea or reasoning in a bit more detail?
>

My take is that XactLockTableWait() isn’t really designed to work on
standby. Instead of adding another layer on top like v4 did, maybe we can
tweak the function itself to support standby. One possible approach could
be to add a check like RecoveryInProgress() to handle the logic when
running on a standby.

Best regards,
Xuneng