Re: max_wal_senders must die

Josh Berkus wrote:
> Well, now that you mention it, I also think that "hot standby" should be
> the default. Yes, I know about the overhead, but I also think that the
> number of our users who want easy replication *far* outnumber the users
> who care about an extra 10% WAL overhead.
>

I think this whole situation is similar to the resistance to increasing
default_statistics_target. There's additional overhead added by
enabling both of these settings, in return for making it more likely for
the average person to see useful behavior by default. If things are
rejiggered so the advanced user has to turn things off in order to get
optimal performance when not using these features, in return for the
newbie being more likely to get things working in basic form, that's
probably a net win for PostgreSQL advocacy. But much like
default_statistics_target, there needs to be some more formal work done
on quantifying just how bad each of these overheads really are first.
We lost 3-7% on multiple simple benchmarks between 8.3 and 8.4[1]
because of that retuning for ease of use on real-world workloads, and
that's not something you want to repeat too often.

[1] http://suckit.blog.hu/2009/09/29/postgresql_history and the tests
Jignesh did while at Sun

--
Greg Smith, 2ndQuadrant US greg(at)2ndQuadrant(dot)com Baltimore, MD
PostgreSQL Training, Services and Support www.2ndQuadrant.us