Re: BUG #18151: pg_upgradecluster fails when column default refers to column

On Sunday, October 8, 2023, PG Bug reporting form <noreply(at)postgresql(dot)org>
wrote:

> The following bug has been logged on the website:
>
> Bug reference: 18151
> Logged by: Liam Morland
> Email address: liam(at)morland(dot)ca
> PostgreSQL version: 15.4
> Operating system: Debian
> Description:
>
> I was trying to upgrade to PG 16:
> pg_upgradecluster 15 main
>
> I got this error:
> pg_restore: error: could not execute query: ERROR: relation "event" does
> not exist
>
> The reason is the the default value for column "event_id" of table "event"
> is "event_id_nextval()". That function is:
> SELECT COALESCE(MAX(event_id) + 1, 1) FROM event;

You are expressly forbidden to have the default value expression of a
column reference a subquery. You must use a trigger. The failure to
prevent the exoressions creation or consistently report such a failure is
the bug, not this. Unfortunately preventing the behavior is not
reasonable, we can only document its forbiddance.

David J.