Christopher Browne <cbbrowne at ca.afilias.info> writes:
> Unfortunately, pg_stat_activity pulls the PIDs from the stats
> collector, so that there is a delay in changes being reported.  (And I
> have seen situations where the stats collector got "blown," in which
> case, this wouldn't report anything even *nearly* correct.)

You are working from obsolete assumptions.  In 8.3 and up,
pg_stat_activity is synchronous and does not depend on the stats
collector at all.  You can't turn it off either (at least, not
with respect to whether a process exists or not).

			regards, tom lane