On Tue, Apr 20, 2010 at 5:02 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> On Tue, Apr 20, 2010 at 2:24 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >>> 3. We'd have to nail pg_authid, pg_auth_members, and their indexes into >>> relcache, because relcache.c isn't prepared to cope otherwise. I doubt >>> this would affect performance in any material way, but it would eat a >>> few more kbytes of storage per backend. > >> Hmm, I'm not sure I understand why this is necessary or what our other >> options are. > > relcache.c assumes that "critical" relations (those for which we have > hard-wired descriptors in schemapg.h) are always nailed-in-cache. In > the general case this is necessary because we'd not be able to rebuild > the cache entry if it got discarded; eg, without a pg_class entry you're > dead in the water. It's possible we could decouple these attributes; > for instance develop a notion of being nailed only until authentication > finishes, or something like that. I'm not thinking it's worth it > though.
Well that just begs the question - why do we need a hard-wired descriptor? Presumably we should only need to hard-wired descriptors for the relations are used by the relcache code itself to build more descriptors - so clearly pg_cache and pg_attribute, but beyond that I don't get it. In particular, I can't see any reason why we couldn't just build the descriptor for pg_authid etc. by scanning pg_class and pg_attribute. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
