Re: Bump default wal_level to logical

On Mon, Jun 8, 2020 at 8:46 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:

> On Mon, Jun 08, 2020 at 11:59:14AM +0530, Amit Kapila wrote:
> > I think we should first do performance testing to see what is the
> > overhead of making this default. I think pgbench read-write at
> > various scale factors would be a good starting point. Also, we should
> > see how much additional WAL it generates as compared to current
> > default.
>
> +1. I recall that changing wal_level to logical has been discussed in
> the past and performance was the actual take to debate on.
>

That was at least the discussion (long-going and multi-repeated) before we
upped it from minimal to replica. There were some pretty extensive
benchmarking done to prove that the difference was very small, and this was
weighed against the ability to take basic backups of the system (which
arguably is more important than being able to do logical replication).

I agree that we should consider changing it *if* it does not come with a
substantial overhead, but that has to be shown.

Of course, what would be even neater would be if it could be changed so you
don't have to bounce the server to change the wal_level. That's a bigger
change though, but perhaps it is now possible once we have the "global
barriers" in 13?

--
Magnus Hagander
Me: https://www.hagander.net/ <http://www.hagander.net/>
Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>