Re: Synchronizing slots from primary to standby - Mailing list pgsql-hackers

From Bertrand Drouvot
Subject Re: Synchronizing slots from primary to standby
Date
Msg-id ZeGAoY6UflxBMUOM@ip-10-97-1-34.eu-west-3.compute.internal
Whole thread Raw
In response to Re: Synchronizing slots from primary to standby  (Peter Smith <smithpb2250@gmail.com>)
List pgsql-hackers
Hi,

On Fri, Mar 01, 2024 at 03:22:55PM +1100, Peter Smith wrote:
> Here are some review comments for v102-0001.
> 
> ======
> doc/src/sgml/config.sgml
> 
> 1.
> +       <para>
> +        Lists the streaming replication standby server slot names that logical
> +        WAL sender processes will wait for. Logical WAL sender processes will
> +        send decoded changes to plugins only after the specified replication
> +        slots confirm receiving WAL. This guarantees that logical replication
> +        slots with failover enabled do not consume changes until those changes
> +        are received and flushed to corresponding physical standbys. If a
> +        logical replication connection is meant to switch to a physical standby
> +        after the standby is promoted, the physical replication slot for the
> +        standby should be listed here. Note that logical replication will not
> +        proceed if the slots specified in the standby_slot_names do
> not exist or
> +        are invalidated.
> +       </para>
> 
> Should this also mention the effect this GUC has on those 2 SQL
> functions? E.g. Commit message says:
> 
> Additionally, The SQL functions pg_logical_slot_get_changes and
> pg_replication_slot_advance are modified to wait for the replication
> slots mentioned in 'standby_slot_names' to catch up before returning.

I think that's also true for all the ones that rely on
pg_logical_slot_get_changes_guts(), means:

- pg_logical_slot_get_changes
- pg_logical_slot_peek_changes
- pg_logical_slot_get_binary_changes
- pg_logical_slot_peek_binary_changes

Not sure it's worth to mention the "binary" ones though as their doc mention
they behave as their "non binary" counterpart.

Regards,

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



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