hubert depesz lubaczewski <depesz(at)depesz(dot)com> writes:
> why backend process from one database has opened files from other databases?
That's not very surprising at all: a backend might have to write out a
dirty buffer in order to reclaim the buffer for re-use, and which
database the page is from doesn't enter into that.
What does seem surprising is that it's had to do that quite a lot.
Is this an old PG version without a bgwriter process? In a properly
functioning recent release, I'd expect only the bgwriter to have a
really eclectic mix of open files.
regards, tom lane