Re: PostgreSQL 16 release announcement draft

Op 8/26/23 om 04:51 schreef Jonathan S. Katz:
> On 8/24/23 11:17 AM, Erik Rijkers wrote:
>> Op 8/24/23 om 16:32 schreef Jonathan S. Katz:
>>> On 8/23/23 5:07 PM, David Rowley wrote:
>>>> On Thu, 24 Aug 2023 at 05:55, Jonathan S. Katz
>>>> <jkatz(at)postgresql(dot)org> wrote:
>>
>> Hi,
>>
>> When v15 docs have:
>>
>> "27.2.7. Cascading Replication
>> The cascading replication feature allows a standby server to accept
>> replication connections and stream WAL records to other standbys,
>> acting as a relay. This can be used to reduce the number of direct
>> connections to the primary and also to minimize inter-site bandwidth
>> overheads."
>>
>> why then, in the release draft, is that capability mentioned as
>> something that is new for v16?
>> "
>> In PostgreSQL 16, users can perform logical decoding from a standby
>> instance, meaning a standby can publish logical changes to other servers.
>> "
>>
>> Is there a difference between the two?
>
> Yes. Those docs refer to **physical** replication, where a standby can
> continue to replicate WAL records to other standbys. In v16, standbys
> can now publish changes over **logical** replication.

Well, I must assume you are right.

But why is the attached program, running 3 cascading v15 servers,
showing 'logical' in the middle server's (port 6526)
pg_replication_slots.slot_type ? Surely that is not physical but
logical replication?

port | svn | slot_name | slot_type
------+--------+--------------------+-----------
6526 | 150003 | pub_6527_from_6526 | logical <--
(1 row)

I must be confused -- I will be thankful for enlightenment.

Erik

> Thanks,
>
> Jonathan
>