Le 28/10/2019 à 17:25, Tom Lane a écrit :
=?UTF-8?Q?Gr=c3=a9goire_de_Turckheim?= <gdeturckheim@xxxxxxxxxxxx> 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.
Let's do it this way, I'll give it a try (might be long, this isn't
something we can easily upgrade) and get back to you.
Thanks!
--
Grégoire de Turckheim
