On Nov 18, 2007 8:29 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
> On Fri, 2007-11-09 at 13:12 -0600, Scott Marlowe wrote:
>
> > Note that my best time was at around 16 Meg work_mem. This data set
> > is MUCH bigger than 16 Meg, it's around 300-400 Meg. But work_mem
> > optimized out at 16 Meg. Btw, I tried it going as high as 768 Meg,
> > and it was still slower than 16M.
>
> Remember that what you have shown is that for *this* dataset 16Mb is the
> optimum value. It is not a recommended value for all cases.
Actually, on this particular machine, it's held true for all the
datasets that are on it.
But I agree that it's only true for those particular datasets, and
more importantly, this machine.
But my real point was that if you haven't tested various settings on
your machine, you don't know if you're helping or hurting with various
changes to work_mem