Re: [HACKERS] Some notes on optimizer cost estimates

"Henry B. Hotz" <hotz(at)jpl(dot)nasa(dot)gov> writes:
>> to be useful for cost estimating. We could make it a parameter like
>> we do for CPU_PAGE_WEIGHT ... but you know and I know that no one
>> ever bothers to adjust those numbers in the field ...

> Couldn't we test some of these parameters inside configure and set
> them there?

If we could figure out a reasonably cheap way of estimating these
numbers, it'd be worth setting up custom values at installation time.

I don't know how to do that --- AFAICS, getting trustworthy numbers by
measurement would require hundreds of meg of temporary disk space and
probably hours of runtime. (A smaller test would be completely
corrupted by kernel disk caching effects.)

But perhaps someone has an idea how to do it.

regards, tom lane