Jerry Sievers <jerry(at)jerrysievers(dot)com> writes:
> At any rate; I'm wondering what possible causes might be responsible
> for pg_stat_activity's underlying functions to lose track of the valid
> process list?
It sounds like the stats collector missed a few "backend quit"
messages. This isn't real surprising: the stats messaging mechanism is
intentionally designed to drop messages under severe load, rather than
slow down backends.
We recently put in a filter that prevents reporting pg_stat_activity
lines for backends that are dead according to the up-to-date list in
shared memory. I don't think that's in 8.0.3 though.
regards, tom lane