relfilenode on 7.2.3

Hi,

I would like to know for all the entries inside pg_class table (except for
shared tables and views), does the relfilenode field always correspond to a
physical file on the disk at a given moment? Could there be any
inconsistency between the table entry and the actual file? Or this is only
true when the database is fresh started up without any active connection?
Or there is no guarantee at all?

Also, I have seen some posts earlier regarding to can't drop a certain table
because of the corrupted database, Tom suggests deleting the entry inside
pg_class. Is that enough for 7.2.3? Will vacuum automatically do the
actual clean up for those unlinked indexes/physical files? I remember once
I have to do something to pg_type or some other tables. If that's not
enough, what other tables I should pay attention to as well?

http://archives.postgresql.org/pgsql-general/2002-10/msg01371.php

Thanks,

--muteki