Hi,
On 11/2/23 1:27 AM, Zhijie Hou (Fujitsu) wrote:
On Tuesday, October 31, 2023 6:45 PM Amit Kapila <amit.kapil...@gmail.com>
wrote:
We have create_replication_slot and drop_replication_slot in repl_gram.y. How
about if introduce alter_replication_slot and handle the 'failover' flag with
that?
The idea is we will either enable 'failover' at the time
create_replication_slot by
providing an optional failover option or execute a separate command
alter_replication_slot. I think we probably need to perform this command
before the start of streaming.
Here is an attempt to achieve the same. I added a new replication command
alter_replication_slot and introduced a walreceiver api walrcv_alter_slot to
execute the command. The subscription will call the api to enable/disable
the failover of the slot on publisher.
The patch disallows altering the failover option for the subscription. But we
could release the restriction by using the following approaches in next version:
I think we will have the following options to allow alter of the 'failover'
property: (a) we can allow altering 'failover' only for the 'disabled'
subscription; to achieve that, we need to open a connection during alter
subscription and change this property of slot; (b) apply worker detects the
change in 'failover' option; run the alter_replication_slot command; this needs
more analysis as apply_worker is already doing streaming and changing slot
property in between could be tricky.
What do you think about also adding a pg_alter_logical_replication_slot() or
such
function?
That would allow users to alter manually created logical replication slots
without
the need to make a replication connection.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
