Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> CASE will be quite bad for optimization, and then you might as well go
> with IS DISTINCT FROM, which is just as bad but simpler.
Definitely avoid CASE if you can. Although the planner currently knows
nothing about IS DISTINCT FROM, that's fixable in principle. We'll
probably never be able to optimize CASE conditions very much because of
their special evaluation rules.
regards, tom lane