> You should have chosen a better foundation. pg_bench is notorious for
> producing results that are (a) nonrepeatable and (b) not relevant to
> a wide variety of situations. All it really tells you about is the
> efficiency of a large number of updates to a small number of rows.
You might want to try -N option of pgbench. It avoids updates to
branches and tellers tables.
--
Tatsuo Ishii