max_connections

I have a two dumb questions.

1)
I know the max_connections value change requires a restart.

I also read a thread, which says why it is the case, assuming it still
holds true.

Jean Arnaud <Jean(dot)Arnaud(at)inrialpes(dot)fr> writes:
> I'm looking for a way to change the "max_connections" parameter without
> restarting the PostGreSQL database.

There is none. That's one of the parameters that determines shared
memory array sizes, and we can't change those on-the-fly.

regards, tom lane

Does that mean, if I set max_connections to 1000 users, but only intend to
use 10 at max (via conn limit per role settings), what would be the perf
difference compared to max_connections = 100 , but still using only 10 at
max.

2)
can i for test purposes.compile src with a xid max value to 2^16 etc ? like
with uint16

Basically, I was trying to simulate xid wraparound, by creating an open
transaction and an inactive replication slot, and then running a huge
parallel loops to bump txid_current() to see what happens at 2B crossover.
it takes forever on my slow laptop.
I do not see these in test scenarios, or could not find any.

as always, ignore if not relevant, or already discussed.
I am preparing for interviews, hence asking myself dumb questions :)

--
Thanks,
Vijay
Mumbai, India