On Tue, 2021-01-26 at 06:57 +0000, PG Doc comments form wrote:
> Page: https://www.postgresql.org/docs/13/pgupgrade.html
> Description:
>
> During the pg_upgrade process, a check is run to make sure
> pg_catalog.pg_roles has only a single non pg_* user, typically this is just
> 'postgres'. If this check fails, the error message is "Only the install user
> can be defined in the new cluster."; This message implies the user executing
> pg_upgrade must match the the rolsuper in pg_catalog.pg_roles.
>
> There's no indication in the documentation that the user table must be
> flushed of all but the one user, nor does it prescribe a method to move
> forward. The error message is not helpful; I only figured it out by finding
> and reading the postgres source code.
The error message says "in the new cluster".
The documentation says, "Initialize the new PostgreSQL cluster" and that there
is no need to start the cluster. That is a pretty strong indication that it
is not necessary to create any objects there.
But perhaps it would not harm to be more explicit and add something like
that:
"Do not create and users, tablespaces or other objects on the new cluster."
Yours,
Laurenz Albe