Re: Time delayed LR (WAS Re: logical replication restrictions)

On Thu, Mar 9, 2023 at 2:56 PM Kyotaro Horiguchi
<horikyota(dot)ntt(at)gmail(dot)com> wrote:
>
> At Thu, 9 Mar 2023 11:00:46 +0530, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote in
> > On Wed, Mar 8, 2023 at 9:20 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > >
> > > On Wed, Mar 8, 2023 at 3:30 AM Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote:
> > > >
> > >
> > > > IMO the current set of
> > > > trade-offs (e.g., unavoidable bloat and WAL buildup) would make this
> > > > feature virtually unusable for a lot of workloads, so it's probably worth
> > > > exploring an alternative approach.
> > >
> > > It might require more engineering effort for alternative approaches
> > > such as one I proposed but the feature could become better from the
> > > user perspective. I also think it would be worth exploring it if we've
> > > not yet.
> > >
> >
> > Fair enough. I think as of now most people think that we should
> > consider alternative approaches for this feature. The two ideas at a
>
> If we can notify subscriber of the transaction start time, will that
> solve the current problem?
>

I don't think that will solve the current problem because the problem
is related to confirming back the flush LSN (commit LSN) to the
publisher which we do only after we commit the delayed transaction.
Due to this, we are not able to advance WAL(restart_lsn)/XMIN on the
publisher which causes an accumulation of WAL and does not allow the
vacuum to remove deleted rows. Do you have something else in mind
which makes you think that it can solve the problem?

--
With Regards,
Amit Kapila.