From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Magnus Hagander <magnus(at)hagander(dot)net> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Defaults for replication/backup |
Date: | 2016-02-13 16:10:58 |
Message-ID: | 22785.1455379858@sss.pgh.pa.us |
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Magnus Hagander <magnus(at)hagander(dot)net> writes:
> On Sat, Feb 13, 2016 at 4:52 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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
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