Re: Synchronizing slots from primary to standby

On Tue, Dec 26, 2023 at 3:00 PM Hayato Kuroda (Fujitsu)
<kuroda.hayato@fujitsu.com> wrote:
>
> > I think we should be able to detect it if we want but do we want to
> > add this restriction considering that users can always install the
> > required plugins after standby gets promoted? I think we can do either
> > way in this case but as we are not going to use these slots till the
> > standby node is promoted, it seems okay to validate the plugins after
> > promotion once users use the synced slots.
>
> Personally it should be detected, but I want to hear opinions from others.
> Below are my reasons:
>
> 1)
> We can avoid a possibility that users miss the installation of plugins. Basically
> we should detect before the issue will really occur.
>
> 2)
> Rules around here might be inconsistent. Slots which will be synchronized can be
> created either way:
>
> a) manual creation via SQL function, or
> b) automatic creation by slotsync worker.
>
> In case of a), the decoding context is created when creation so that the plugin
> must be installed. Case b), however, we allow not to install beforehand. I felt
> it might be confused for users. Thought?
>

I think the (a) way could lead to the setting of incorrect LSNs
(restart_LSN and confirmed_flush_lsn) considering they are not copied
from the primary.

--
With Regards,
Amit Kapila.