Re: Super Optimizing Postgres

Bruce Momjian wrote:
> 
> > Didn't Bruce do a document on this exact topic?  I'm not sure it's everything
> > you are looking for, but it might help you get started.
> 
> Sure:
> 
>         http://techdocs.postgresql.org

Question:

Does sort memory come out of shared? I don't think so (would it need too?), but
"Cache Size and Sort Size " seems to imply that it does.

Also, you don't go into the COST variables. If what is documented about them is
correct, they are woefully incorrect with a modern machine.

Would a 1.3 ghz Athlon really have a cpu_operator_cost of 0.0025? That would
imply that that computer could process 2500 conditionals in the time it would
take to make a sequential read. If Postgres is run on a 10K RPM disk vs a 5.4K
RPM disk on two different machines with the same processor and speed, these
numbers can't hope to be right, one should be about twice as high as the other.

That said, do these numbers really affect the planner all that much?