Re: preserving db/ts/relfilenode OIDs across pg_upgrade (was Re: storing an explicit nonce)

On Fri, Jan 21, 2022 at 1:08 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Thu, Jan 20, 2022 at 11:03 AM Shruthi Gowda <gowdashru(at)gmail(dot)com> wrote:
> > It is not required for PostgresObjectId. The unused_oids script
> > provides a list of unused oids in the manually-assignable OIDs range
> > (1-9999).
>
> Well, so ... why are we not treating the OIDs for these two databases
> the same? If there's a range from which we can assign OIDs without
> risk of duplication and without needing to update this script, perhaps
> we ought to assign both of them from that range and leave the script
> alone.

From what I see in the code, template0 and postgres are the last
things that get created in initdb phase. The system OIDs that get
assigned to these DBs vary from release to release. At present, the
system assigned OIDs of template0 and postgres are 13679 and 13680
respectively. I feel it would be safe to assign 16000 and 16001 for
template0 and postgres respectively from the unpinned object OID range
12000 - 16383. In the future, even if the initdb unpinned objects
reach the range of 16000 issues can only arise if initdb() creates
another system-created database for which the system assigns these
reserved OIDs (16000, 16001).

> + * that is in use in the old cluster is also used in th new cluster - and
>
> th -> the.

Fixed

> +preserves the DB, tablespace, relfilenode OIDs so TOAST and other references
>
> Insert "and" before "relfilenode".

Fixed

Attached is the latest patch for review.

Shruthi KC
EnterpriseDB: http://www.enterprisedb.com