Re: Use of index in 7.0 vs 6.5

Tom Lane wrote:

> Ryan Bradetich <ryan_bradetich(at)hp(dot)com> writes:
> > This worked great! Is their a place I can change the default to 3?
> > I do not want to change all the scripts to include this :)
>
> See src/include/optimizer/cost.h. However, I am currently thinking of
> taking Hiroshi's advice instead. Lowering RANDOM_PAGE_COST seems like
> a bad idea --- if anything, we might want to raise it ;-)
>
> >>>> Or how about changing current fudge factor ?
> >>>> For example,from 0.5 to 0.2 which is the fudge factor of attdisbursion
> >>>> calculation.
> >>
> >> Yes, that's another way --- and probably more defensible than changing
> >> random_page_cost, now that I think about it. Unfortunately it's a
> >> hardwired constant and so not as easily experimented with :-(.
>
> > Can you give me more information about this? I do not have a problem
> > re-compiling the database and performing more testing if you would like.
>
> The fudge factor in question is currently 0.5, and is used in two places
> in src/backend/utils/adt/selfuncs.c (looks like lines 193 and 212 in 7.0
> sources). I was thinking of dropping it to 0.25 or 0.1.
>
> regards, tom lane

Tom and Hiroshi,

I modified the backend to 0.1 and this has been working great! Thanks
again for the suggestion, and I'll let you know if we run into a problem.

Thanks again!

Ryan