Re: relfilenode

On Thu, Oct 27, 2005 at 09:12:15PM -0400, Andrew Dunstan wrote:
> The docs have this description for pg_class::relfilenode: "Name of the
> on-disk file of this relation; 0 if none". However, Elein just pointed
> out to me that there are no entries with 0, so this description seems
> incorrect. What should we say? It appears that in at least some of these
> cases the value is the same as the oid.

Is 0 a legitimate value now that pg_xactlock is gone? In pre-8.1
clusters that's the only relation I see with relfilenode 0, but
maybe that's just because I don't have anything defined that would
have relfilenode 0 (what, if anything, would?).

Composite types have relfilenode set even though they don't appear
to have an on-disk file -- should they be 0?

Based on what I've seen I've assumed that relfilenode starts out
the same as oid but can change if you do something that rewrites
the table (truncate, cluster, alter column type, etc.). I haven't
dug into the code to confirm that, though.

--
Michael Fuhr