Re: Turn off vacuum in pgbench?

On Tue, 25 Sep 2007, Tatsuo Ishii wrote:

> Now that PostgreSQL 8.3 enables autovacuum by default, I think pgbench
> should stop issuing vacuum in pgbench -i since an ordinary vacuum will
> take very long time under autovacuum running. If there's no objection,
> I will remove vacuum from pgbench.

Just removing the vacuum might cause backwards test repeatability issues
for some people, and fixing all the issues in this area will take a bigger
change than you're suggesting. There are already the -n and -v parameters
to adjust what gets vacuumed and what doesn't, and if you just read the
documentation on those it's really confusing. I had to look at the source
code to fully understand what they did.

I think you're right that something should be done to pgbench to address
that a default auto-vacuum configuration is going to change how some
people want to run the tool, but I don't think it's as simple as "remove
vacuum from pgbench"; in order to have a smooth transition, I'd want to
see the old behavior still available. If the default changes, that would
require inverting the command line switches, and now you're talking about
a much messier change.

Because of that, I personally wouldn't touch anything in the code at this
late point in the 8.3 cycle. An update to the documentation to clarify
how you might change the use of -n/-v based on whether autovaccum is
turned on, and hopefully improving the description of both those switches
in the process, would be a welcome improvement, and I could help out with
that.

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD