Re: Optimize LISTEN/NOTIFY

On Tue, Sep 23, 2025, at 18:27, Tom Lane wrote:
> I concur that these are orthogonal issues, but I don't understand
> why you withdrew your patches --- don't they constitute a solution
> to the first scalability bottleneck?

Thanks for getting back to this thread. I was unhappy with not finding a
solution that would improve all use-cases, I had a feeling it would be
possible to find one, and I think I've done so now.

>> I guess my main question is if we think we should fix one problem first,
>> then the other, both at the same time, or only one or the other?
>
> I imagine we'd eventually want to fix both, but it doesn't have to
> be done in the same patch.

I've attached a new patch with a new pragmatic approach, that
specifically addresses the context switching cost.

The patch is based upon the assumption that some extra LISTEN/NOTIFY
latency would be acceptable by most users, as a trade-off, in order to
improve throughput.

One nice thing with this approach is that it has the potential to
improve throughput both for users with just a single listening backend,
and also for users with lots of listening backends.

More details in the commit message of the patch.

Curious to hear thoughts on this approach.

/Joel