Tom Lane wrote:
>
> BTW, I'm thinking that a "cost constant" probably ought to be measured
> in units of cpu_operator_cost. The default for built-in functions would
> thus be 1, at least till such time as someone wants to refine the
> estimates. We'd probably want the default for PL and SQL functions to
> be 10 or 100 or so.
Any chance that costs could eventually change to real-world units?
It's hard for me to guess how many cpu_operator_cost units
something might take; but relatively easy for me to measure
or estimate in fractions-of-a-seconds how long something takes.
I could imagine having the other planner costs be measured in seconds
too - perhaps with the goal of eventually writing some auto-config
code that tries to measure values like cpu_tuple_cost on a given
piece of hardware.
