$sub proposed in a nearby thread. Looks like we have a consensus that
$subj is beneficial.
I implemented necessary legwork, namely a clock-based check in the
wait() routine, PFA. I'm not sure the default pg_sleep argument of 50
millisecond is good, but it is fast enough to not spot any difference
in by-hand testing.
[0] https://www.postgresql.org/message-id/aKT7qD0VkGhQgFJe%40paquier.xyz
--
Best regards,
Kirill Reshke