Re: Identifying user-created objects

On Thu, Feb 13, 2020 at 8:32 AM Amit Langote <amitlangote09@gmail.com> wrote:
>
> On Thu, Feb 13, 2020 at 10:30 AM Kyotaro Horiguchi
> <horikyota.ntt@gmail.com> wrote:
> > At Mon, 10 Feb 2020 14:32:44 +0900, Amit Langote <amitlangote09@gmail.com> wrote in
> > > Agree that ObjectIsUserObject(oid) is easier to read than oid >=
> > > FirstNormalObject.  I would have not bothered, for example, if it was
> > > something like oid >= FirstUserObjectId to begin with.
> >
> > Aside from the naming, I'm not sure it's sensible to use
> > FirstNormalObjectId since I don't see a clear definition or required
> > characteristics for "user created objects" is.  If we did CREATE
> > TABLE, FUNCTION or maybe any objects during single-user mode before
> > the first object is created during normal multiuser operation, the
> > "user-created(or not?)" object has an OID less than
> > FirstNormalObjectId. If such objects are the "user created object", we
> > need FirstUserObjectId defferent from FirstNormalObjectId.
>
> Interesting observation.  Connecting to database in --single mode,
> whether done using initdb or directly, is always considered
> "bootstrapping", so the OIDs from the bootstrapping range are
> consumed.
>
> $ postgres --single -D pgdata postgres
>
> PostgreSQL stand-alone backend 13devel
> backend> create table a (a int);
> backend> select 'a'::regclass::oid;
>          1: oid (typeid = 26, len = 4, typmod = -1, byval = t)
>         ----
>          1: oid = "14168"       (typeid = 26, len = 4, typmod = -1, byval = t)
>
> Here, FirstBootstrapObjectId < 14168 < FirstNormalObjectId

FTR it's also possible to get the same result using binary mode and
binary_upgrade_set_next_XXX functions.

> Maybe we could document that pg_is_user_object() and its internal
> counterpart returns true only for objects that are created during
> "normal" multi-user database operation.

+1