Josh Berkus <josh@agliodbs.com> writes:
> What I'd like to do is implement the constant method for 8.2, and work on
> doing the S() method later on. Does that make sense?
I'm not thrilled with putting in a stopgap that we will have to support
forever. The constant method is *clearly* inadequate for many (probably
most IMHO) practical cases. Where do you see it being of use?
W.R.T. the estimator function method, the concern about recursion seems
misplaced. Such an estimator presumably wouldn't invoke the associated
function itself. I'm more concerned about coming up with a usable API
for such things. Our existing mechanisms for estimating operator
selectivities require access to internal planner data structures, which
makes it pretty much impossible to write them in anything but C. We'd
need something cleaner to have a feature I'd want to export for general
use.
regards, tom lane