Michael,
> So What does memcached offer pgsql users? It would still seem to offer
> the benefit of a multi-machined cache.
Yes, and a very, very fast one too ... like, 120,000 operations per second.
PostgreSQL can't match that because of the overhead of authentication,
security, transaction visibility checking, etc.
So memcached becomes a very good place to stick data that's read often but not
updated often, or alternately data that changes often but is disposable. An
example of the former is a user+ACL list; and example of the latter is web
session information ... or simple materialized views.
--
Josh Berkus
Aglio Database Solutions
San Francisco