Re: Statistics Import and Export

Oy.  Those are outright horrid, even without any consideration of
pre-preparing them.  We know the OID of the table we want to dump,
we should be doing "FROM pg_class WHERE oid = whatever" and lose
the join to pg_namespace altogether.  The explicit casts to regclass
are quite expensive too to fetch information that pg_dump already
has.  It already knows the server version, too.

Moreover, the first of these shouldn't be a separate query at all.
I objected to fetching pg_statistic content for all tables at once,
but relpages/reltuples/relallvisible is a pretty small amount of
new info.  We should just collect those fields as part of getTables'
main query of pg_class (which, indeed, is already fetching relpages).

On the second one, if we want to go through the pg_stats view then
we can't rely on table OID, but I don't see why we need the joins
to anything else.  "WHERE s.schemaname = 'x' AND s.tablename = 'y'"
seems sufficient.

I wonder whether we ought to issue different queries depending on
whether we're superuser.  The pg_stats view is rather expensive
because of its security restrictions, and if we're superuser we
could just look directly at pg_statistic.  Maybe those checks are
fast enough not to matter, but ...