Re: [HACKERS] Some notes on optimizer cost estimates

Tom Lane wrote:

> As best I can measure on my hardware, the cost of a nonsequential
> disk read should be estimated at 4 to 5 times the cost of a sequential
> one --- I'm getting numbers like 2.2 msec per disk page for sequential
> scans, and as much as 11 msec per page for index scans.  I don't
> know, however, if this ratio is similar enough on other platforms
> 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 ...

Would it be possible to place those parameters as run-time
settings and then write a utility that can ship with the
distribution to determine those values? Kind of a self-tuning
utility? 

Mike Mascari