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Subject: Re: Guidance Needed for PostgreSQL Upgrade from 12 to 15
From: Scott Ribe <scott_ribe@elevated-dev.com>
In-Reply-To: <0b8c1b80-93f5-40a7-b67b-19e58207c12c@cloud.gatewaynet.com>
Date: Mon, 18 Nov 2024 12:20:59 -0700
Cc: pgsql-admin@lists.postgresql.org
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To: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
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> On Nov 18, 2024, at 12:10=E2=80=AFPM, Achilleas Mantzios =
<a.mantzios@cloud.gatewaynet.com> wrote:
>=20
>=20
> I'd like to add if someone can tolerate some seconds of downtime, with =
logical replication it is possible to swap the roles of publisher / =
subscriber so that one can keep the old database as a means of extra =
safety. If his/her app breaks beyond repair and there is no time for =
fixing, one can simply go back to the old DB with some minor adjustments =
(such as sequences).

In the same vein, if one's file system offers atomic snapshots:

1) shut down PG
2) run pg_upgrade with the hard links option
3) take snapshot
4) start up new PG

Now, if there's a failure, you can go back to the snapshot and either =
start up the old PG, or do some troubleshooting and try upgrading again.