Re: Synchronizing slots from primary to standby

Hi,

On Thu, Mar 14, 2024 at 02:22:44AM +0000, Zhijie Hou (Fujitsu) wrote:
> Hi,
> 
> Since the standby_slot_names patch has been committed, I am attaching the last
> doc patch for review.
> 

Thanks!

1 ===

+   continue subscribing to publications now on the new primary server without
+   any data loss.

I think "without any data loss" should be re-worded in this context. Data loss
in the sense "data committed on the primary and not visible on the subscriber in
case of failover" can still occurs (in case synchronous replication is not used).

2 ===

+   If the result (failover_ready) of both above steps is
+   true, existing subscriptions will be able to continue without data loss.
+  

I don't think that's true if synchronous replication is not used. Say,

- synchronous replication is not used
- primary is not able to reach the standby anymore and standby_slot_names is set
- new data is inserted into the primary
- then not replicated to subscriber (due to standby_slot_names)

Then I think the both above steps will return true but data would be lost in
case of failover.

Regards,

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