Re: Logical replication timeout problem

On Mon, Apr 18, 2022 at 9:29 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Thu, Apr 14, 2022 at 5:52 PM Euler Taveira <euler(at)eulerto(dot)com> wrote:
> >
> > On Wed, Apr 13, 2022, at 7:45 AM, Amit Kapila wrote:
> >
> > Sawada-San, Euler, do you have any opinion on this approach? I
> > personally still prefer the approach implemented in v10 [1] especially
> > due to the latest finding by Wang-San that we can't update the
> > lag-tracker apart from when it is invoked at the transaction end.
> > However, I am fine if we like this approach more.
> >
> > It seems v15 is simpler and less error prone than v10. v10 has a mix of
> > OutputPluginUpdateProgress() and the new function update_progress(). The v10
> > also calls update_progress() for every change action in pgoutput_change(). It
> > is not a good approach for maintainability -- new changes like sequences need
> > extra calls.
> >
>
> Okay, let's use the v15 approach as Sawada-San also seems to have a
> preference for that.
>
> > However, as you mentioned there should handle the track lag case.
> >
> > Both patches change the OutputPluginUpdateProgress() so it cannot be
> > backpatched. Are you planning to backpatch it? If so, the boolean variable
> > (last_write or end_xacts depending of which version you are considering) could
> > be added to LogicalDecodingContext.
> >
>
> If we add it to LogicalDecodingContext then I think we have to always
> reset the variable after its use which will make it look ugly and
> error-prone. I was not thinking to backpatch it because of the API
> change but I guess if we want to backpatch then we can add it to
> LogicalDecodingContext for back-branches. I am not sure if that will
> look committable but surely we can try.
>

Even, if we want to add the variable in the struct in back-branches,
we need to ensure not to change the size of the struct as it is
exposed, see email [1] for a similar mistake we made in another case.

[1] - https://www.postgresql.org/message-id/2358496.1649168259%40sss.pgh.pa.us

--
With Regards,
Amit Kapila.