Re: [HACKERS] Anyone working on asynchronous NOTIFY reception?

> The biggest problem is that if you have many clients listening on the same
> thing they are signaled at the same time and all of them try to access the
> pg_listener table for write. The result is that you have a lot of waits on
> the table and sometimes also deadlocks if you don't do things carefully.

Right, I recall seeing some things about that in the mailing list
archives (from you, no doubt?).  I had the impression that async.c
had been changed to handle this better as of the current release.
Is there still a problem?

(Fortunately, I don't expect a *lot* of clients waiting on the same
table, but deadlock would still be very bad news...)

> From the Tcl side, a better solution would be to define a tcl event handler,
> like the standard Tcl filehandler, which would be invoked automatically by
> the Tk event loop or by tkwait if using pure Tcl.

I agree.

I don't have an immediate need for Tcl-based clients, so I was just
going to revise libpg and libpg++.  Do you want to redo libpgtcl?
I'd probably get to that eventually, but splitting the work sounds
better :-).

I'll post something later today about what the extensions to the
libpg API should look like.

> I have also some new patches which try to reduce the notify overhead by
> avoiding unnecessary unlocks of the table. If you are interested I can
> post them.

Please do.

            regards, tom lane