Re: Synchronizing slots from primary to standby

Hi,

On 12/8/23 10:06 AM, Amit Kapila wrote:
> On Wed, Dec 6, 2023 at 4:53 PM shveta malik <shveta.malik@gmail.com> wrote:
>>
>> PFA v43, changes are:
>>
> 
> I wanted to discuss 0003 patch about cascading standby's. It is not
> clear to me whether we want to allow physical standbys to further wait
> for cascading standby to sync their slots. If we allow such a feature
> one may expect even primary to wait for all the cascading standby's
> because otherwise still logical subscriber can be ahead of one of the
> cascading standby.

I've the same feeling here. I think it would probably be expected that
the primary also wait for all the cascading standby.

> I feel even if we want to allow such a behaviour we
> can do it later once the main feature is committed. 

Agree.

> I think it would
> be good to just allow logical walsenders on primary to wait for
> physical standbys represented by GUC 'standby_slot_names'.

That makes sense for me for v1.

> If we agree
> on that then it would be good to prohibit setting this GUC on standby
> or at least it should be a no-op even if this GUC should be set on
> physical standby.

I'd prefer to completely prohibit it on standby (to make it very clear it's not
working at all) as long as one can enable it without downtime once the standby
is promoted (which is the case currently).

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com