Re: implementing NOTIFY with message parameter

On Thu, May 12, 2005 at 10:48:50AM -0400, Tom Lane wrote:
> Alvaro Herrera <alvherre(at)surnet(dot)cl> writes:
> > On Thu, May 12, 2005 at 10:09:23AM -0400, Tom Lane wrote:
> >> Please review the archived discussions about reimplementing NOTIFY using
> >> only shared memory, no tables.
>
> > Maybe this can be done using two SLRU areas like we did for multixact.
>
> If you are looking for an existing tool to adapt, I think the sinval
> messaging mechanism is a FAR better prototype.

Hmm. The problem is that it's easy to do something if the sinval queue
fills up -- just reset everybody's cache. But you can't just drop all
pending notifies if the queue fills up.

A possible approach to that problem would be spilling to disk the
entries of the idle backends.

--
Alvaro Herrera (<alvherre[a]surnet.cl>)
"[PostgreSQL] is a great group; in my opinion it is THE best open source
development communities in existence anywhere." (Lamar Owen)