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@gregsmith.com http://www.gregsmith.com Baltimore, MD