Re: Duplicated oids between tables - problem or not?

On Mon, Nov 26, 2012 at 5:04 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Magnus Hagander <magnus@hagander.net> writes:
>> I noticed after a pg_upgrade on a system, that the same oid is used
>> both for a database and a user (repeated many times for different
>> combinations of databases and users). This is because pg_upgrade
>> doesn't preserve the database oid, and it reused the oid of the row in
>> pg_authid.
>
>> The reason I noticed this was that it confuses the hell out of
>> pgadmin. This is clearly a bug in a SQL query pgadmin uses, and I'm
>> going to go fix that.
>
>> But is this something that can cause us problems somewhere else in the
>> system? ISTM the same thing could happen after oid wraparound, but
>> that pg_upgrade makes it a lot more likely to happen. So I'm thinking
>> it shouldn't be a problem since the oid's are in different tables, but
>> are there any other parts of the system where this could cause an
>> actual problem?
>
> It should not.  It's been understood for many years that uniqueness of
> OIDs is only guaranteed within individual catalogs (by means of their
> unique indexes on OID).  That's why mechanisms like pg_depend and
> pg_description use catalog OID + object OID to identify objects.

That's what I figured. The problem with pgadmin is it joins to
pg_shdescription without restricting it on the catalog oid.


> We do insist that hand-assigned OIDs be globally unique, but that's just
> for maintainers' sanity not because the code depends on it.

Gotcha. Thanks!

--Magnus HaganderMe: http://www.hagander.net/Work: http://www.redpill-linpro.com/