Andres Freund <andres@anarazel.de> writes:
> I'm not too worried about that scenario. If, for a cheap plan, the
> planner ends up with a seqscan despite it being disabled, you're pretty
> close to randomly choosing plans already, as the pruning doesn't work
> well anymore (as the %1 percent fuzz factor in
> compare_path_costs_fuzzily() swamps the actual plan costs).
Something I've wanted to do for awhile is to get rid of disable_cost
in favor of pruning disabled plans through logic rather than costing.
I've looked at this once or twice, and it seems doable but not entirely
trivial --- the sticky bits are places where you do need to allow a
disabled plan type because there's no other alternative. But if we
could get that done, it'd help with this sort of problem.
regards, tom lane