Re: Defaults for replication/backup

Magnus Hagander <magnus@hagander.net> writes:
> On Sat, Feb 13, 2016 at 4:52 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> It would be easier to sell this if we had some numbers for the amount of
>> overhead it would add for people *not* using the features.  I do not think
>> I've ever seen, eg, pgbench results with different wal_level and all else
>> the same.

> That's going to be extremely workload dependent. For example, I'd expect
> the overhead to be very close to 0 on a pgbench SELECT only benchmark :)

> The big thing is, IIRC, that we turn off the optimizations in
> min_wal_level. *most* people will see no impact of their regular
> application runtime from that, but it might definitely have an effect on
> data loads and such. For normal runtime, there should be very close to zero
> difference, no?

I was asking for a demonstration of that, not just handwaving.  Even if
it was measured years ago, I wouldn't assume the comparison would be
the same on current Postgres.
        regards, tom lane