Here's a completely different idea. How about we add an option that
means "vacuum this table before running the test" (can be given several
times); by default the set of vacuumed tables is the current pgbench_*
list, but if -f is specified then the default set is cleared. So if you
have a -f script and want to vacuum the default tables, you're forced to
give a few --vacuum-table=foo options. But this gives the option to
vacuum some other table before the test, not just the pgbench default
ones.
This is a bit more complicated, and makes life more difficult to people
using -f and the default pgbench tables than your proposed new -k
switch. But it's more general and it might have more use cases; and
people using -f with the default pgbench tables are probably rare,
anyway.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services