On 31 December 2016 at 15:00, Magnus Hagander <magnus@hagander.net> wrote: > Cycling back to this topic again, but this time at the beginning of a CF. > > Here's an actual patch to change: > > > max_wal_senders=10 > max_replication_slots=20
+1
If that doesn't fly, it seems easy enough to introduce a "min_reserve_limit" GUC that defaults to 10 that gives a lower bound on the amount of memory we reserve for many of those shmem allocs; that can be set to 0 for people that want the old behaviour. Then we can allow changes up to the memory limit without a restart.
> wal_level=replica
This is more problematic because it changes behaviours.
You can't actually change the other two without changing wal_level.
A more useful approach would be to bring all the things needed to enable replication into one ALTER SYSTEM command, so people have just one thing they need to execute and it will work out the details and locations for you. That way we can maintain the defaults yet make it easier to enable in a useful way.
Sure, that would be great - the core being the ability to change these things without a restart. But I would argue for not letting perfection get in the way of progress, and do this anyway. I doubt there is any way the bigger change is going to get done for 10 at this point, so we should give people the ability to do backups off a default installation already.