Re: Notifications within triggers seem to compromise performance

=?UTF-8?Q?Gr=c3=a9goire_de_Turckheim?= <gdeturckheim(at)scaleway(dot)com> writes:
> Le 28/10/2019 à 15:22, Tom Lane a écrit :
>> We made some performance improvements for NOTIFY just a couple months
>> ago, cf commits b10f40bf0, bb5ae8f6c, bca6e6435, 51004c717. It would
>> be interesting to know how much those changes helped your use-case.

> If my understanding of the problem is correct, there is no performance
> issue with the notification itself.
> The problem is the following: a system-wide lock is taken pre-commit, so
> any other transaction with a NOTIFY will have to wait for other
> transactions to complete before it can leave its own pre-commit stage.

Right, but all commits are single-threaded at some granularity.
The big problem with NOTIFY is that it sits for a long time holding
that lock, if you have a lot of notify traffic. The commits I mentioned
should improve that.

Anyway, as I said, it would be good to find out whether the already
finished fixes are enough to solve your problem, before we debate
whether more needs to be done.

regards, tom lane