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. ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend