Experimenting with hash tables inside pg_dump

Today, pg_dump does a lot of internal lookups via binary search
in presorted arrays. I thought it might improve matters
to replace those binary searches with hash tables, theoretically
converting O(log N) searches into O(1) searches. So I tried making
a hash table indexed by CatalogId (tableoid+oid) with simplehash.h,
and replacing as many data structures as I could with that.

This makes the code shorter and (IMO anyway) cleaner, but

(a) the executable size increases by a few KB --- apparently, even
the minimum subset of simplehash.h's functionality is code-wasteful.

(b) I couldn't measure any change in performance at all. I tried
it on the regression database and on a toy DB with 10000 simple
tables. Maybe on a really large DB you'd notice some difference,
but I'm not very optimistic now.

So this experiment feels like a failure, but I thought I'd post
the patch and results for the archives' sake. Maybe somebody
will think of a way to improve matters. Or maybe it's worth
doing just to shorten the code?

regards, tom lane