Re: Expected accuracy of planner statistics

[Arturo Perez <aperez(at)hayesinc(dot)com>]

In article <20060929010011(dot)GQ34238(at)nasby(dot)net>,
 jim(at)nasby(dot)net ("Jim C. Nasby") wrote:

> The problem is that you can't actually get
> a good n_distinct estimate if you're sampling less than a very large
> chunk of the table. Since our sampling maxes out at something like 30k
> pages, at some point the n_distinct estimates just degrade. :(

Can the DBA just set n_distinct?  Sometimes s/he just knows what the 
value should be.

Then, of course, the questions becomes how to keep vacuum et al from 
messing it up.

-arturo