Re: listen/notify argument (old topic revisited)

Hannu Krosing <hannu(at)tm(dot)ee> writes:
> Perhaps this is a good place to introduce anonymous mmap ?

I don't think so; it just adds a portability variable without buying
us anything.

> Is there a way to grow anonymous mmap on demand ?

Nope. Not portably, anyway. For instance, the HPUX man page for mmap
sayeth:

If the size of the mapped file changes after the call to mmap(), the
effect of references to portions of the mapped region that correspond
to added or removed portions of the file is unspecified.

Dynamically re-mmapping after enlarging the file might work, but there
are all sorts of interesting constraints on that too; it looks like
you'd have to somehow synchronize things so that all the backends do it
at the exact same time.

On the whole I see no advantage to be gained here, compared to the
implementation I sketched earlier with a fixed-size shared buffer and
enlargeable internal buffers in backends.

regards, tom lane