Re: Move defaults toward ICU in 16?

Hi,

On 2023-02-17 12:36:05 -0800, Jeff Davis wrote:
> > > There's already a check that the new cluster is empty, so I think
> > > it's
> > > safe to hack the pg_database locale fields.
> >
> > I don't think we need to, we do issue the CREATE DATABASEs. So we
> > just need to
> > make sure that includes the collation provider info, and the proper
> > template
> > database, in pg_upgrade mode.
>
> We must fixup template1/postgres in the new cluster (change it to libc
> to match the old cluster), because any objects existing in those
> databases in the old cluster may depend on the default collation. I
> don't see how we can do that without updating pg_database, so I'm not
> following your point.

I think we just drop/recreate template1 and postgres during pg_upgrade. Yep,
looks like it. See create_new_objects():

/*
* template1 database will already exist in the target installation,
* so tell pg_restore to drop and recreate it; otherwise we would fail
* to propagate its database-level properties.
*/
create_opts = "--clean --create";

and then:

/*
* postgres database will already exist in the target installation, so
* tell pg_restore to drop and recreate it; otherwise we would fail to
* propagate its database-level properties.
*/
if (strcmp(old_db->db_name, "postgres") == 0)
create_opts = "--clean --create";
else
create_opts = "--create";

Greetings,

Andres Freund