Re: speed up a logical replica setup

On Tue, Apr 30, 2024 at 12:04 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Mon, Apr 29, 2024 at 5:28 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Mon, Apr 29, 2024 at 5:23 PM Euler Taveira <euler(at)eulerto(dot)com> wrote:
> >
>
> I was trying to test this utility when 'sync_replication_slots' is on
> and it gets in an ERROR loop [1] and never finishes. Please find the
> postgresql.auto used on the standby attached. I think if the standby
> has enabled sync_slots, you need to pass dbname in
> GenerateRecoveryConfig().

The other possibility is that when we start standby from
pg_createsubscriber, we specifically set 'sync_replication_slots' as
false.

>
> I couldn't test it further but I wonder if
> there are already synced slots on the standby (either due to
> 'sync_replication_slots' or users have used
> pg_sync_replication_slots() before invoking pg_createsubscriber),
> those would be retained as it is on new subscriber and lead to
> unnecessary WAL retention and dead rows.
>

This still needs some handling.

BTW, I don't see the use of following messages in --dry-run mode or
rather they could be misleading:
pg_createsubscriber: hint: If pg_createsubscriber fails after this
point, you must recreate the physical replica before continuing.
...
...
pg_createsubscriber: setting the replication progress (node name
"pg_0" ; LSN 0/0) on database "postgres"

Similarly, we should think if below messages are useful in --dry-run mode:
pg_createsubscriber: dropping publication
"pg_createsubscriber_5_887f7991" on database "postgres"
pg_createsubscriber: creating subscription
"pg_createsubscriber_5_887f7991" on database "postgres"
...
pg_createsubscriber: enabling subscription
"pg_createsubscriber_5_887f7991" on database "postgres"

--
With Regards,
Amit Kapila.