Re: Performance

Claudio Freire <klaussfreire@gmail.com> writes:
> On Wed, Apr 13, 2011 at 4:32 PM, Kevin Grittner
> <Kevin.Grittner@wicourts.gov> wrote:
>> If you model the costing to reflect the reality on your server, good
>> plans will be chosen.

> Wouldn't it be "better" to derive those costs from actual performance
> data measured at runtime?

> Say, pg could measure random/seq page cost, *per tablespace* even.

> Has that been tried?

Getting numbers that mean much of anything is a slow, expensive
process.  You really don't want the database trying to do that for you.
Once you've got them, you *really* don't want the database
editorializing on them.

            regards, tom lane