Re: planner costs in "warm cache" tests

On 2010-05-30 20:34, Tom Lane wrote:
> Jesper Krogh<jesper@krogh.cc>  writes:
>
>> testdb=# set seq_page_cost = 0.00001;
>> SET
>> testdb=# set random_page_cost = 0.00001;
>> SET
>>
> Well, hmm, I really doubt that that represents reality either.  A page
> access is by no means "free" even when the page is already in cache.
> I don't recall anyone suggesting that you set these numbers to less
> than perhaps 0.01.
>
>
Thank you for the prompt response. Is it a "false assumption" that the
cost should in some metric between different plans be a measurement
of actual run-time in a dead-disk run?

It should most likely be matching a typical workload situation, but that
it really hard to tell anything about, so my "feeling" would be that the
dead disk case is the one closest?

--
Jesper