Re: Questions on Upgrading PostgreSQL from 15.0 to 15.9 and Setting Up Streaming Replication

On Sun, Nov 24, 2024 at 11:05 AM Subhash Udata <subhashudata(at)gmail(dot)com>
wrote:

> Dear PostgreSQL Community,
>
> I have a production database setup with a primary server and a standby
> server. The database is currently running on *PostgreSQL 15.0*, and I
> plan to upgrade both servers to *15.9*.
>
> I have the following questions regarding the upgrade and replication
> process:
>
> 1.
>
> *Upgrade and Replication Compatibility*:
> - My plan is to perform a failover, promote the standby server
> (currently 15.0) to primary, and then upgrade the old primary server to
> version 15.9.
>
>
Try to replicate from old->new version, because bug fixes in newer versions
might have broken something in new->old replication.

If you really can't tolerate any downtime, then shutdown and upgrade the
Secondary server from 15.0 to 15.10. Once you start it back up,
replication from the still-15.0 primary will catch back up to the
now-patched Secondary.

Fail over to the Secondary (now new-Primary), and then patch old-Primary to
15.10.

>
> 1.
> - After upgrading the old primary server to version 15.9, I want to
> configure it as a standby server and set up streaming replication with the
> new primary server, which will still be running version 15.0.
> - Is it possible to establish streaming replication between these
> two versions (*15.0* as primary and *15.9* as standby)?
> 2.
>
> *Efficient Replication Setup*:
> - The production database is around *1TB in size*, and creating
> replication using pg_basebackup is taking more than 2–3 hours to
> complete.
> - Is there an alternative method to set up replication without
> taking a full backup of the entire cluster but instead using only the WAL
> files that have changed on both servers?
>
>
pg_rewind is probably what you want. I've never used it, though.

--
Death to <Redacted>, and butter sauce.
Don't boil me, I'm still alive.
<Redacted> lobster!