Re: LISTEN vs. two-phase commit

"Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> writes:
> Tom Lane wrote:
>> "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> writes:
>>> To be honest, I didn't realize the receiver gets to know the PID of the
>>> sending process, but clearly it does. It seems mostly indifferent to me;
>>> it's not guaranteed that the PID is valid by the time the client
>>> application sees it anyway.
>>
>> Well, with the current definition it is; but that seems like a point
>> against trying to send the original PID.

> There's a small window between backend A committing and sending a
> NOTIFY, and the time client B receives the notification from backend B
> through the connection and reacts to it.

Sorry, I was unclear: the case that's of interest is telling
self-notifies apart from others. For this purpose, your own backend's
PID *is* sufficiently stable, because you're still connected to it
when the notify is sent to you.

> This is all very hand-wavy of course, as we don't know of any real
> application that uses LISTEN/NOTIFY with 2PC...

Yeah. I'm inclined to leave that alone (but document it) until/unless
someone complains. Without a real use-case to look at, it's a bit hard
to be sure what's a useful behavior.

regards, tom lane