Pavel Stehule <pavel.stehule@gmail.com> writes:
> "unnest" returns all fields, but
> these fields should not be used. There isn't possible to say - stop, I
> don't need other fields. It's possible just with special PL statement,
> because it is controlled by PL. So it is reason why I don't believe in
> optimizations on PL level.
That is complete nonsense. array_unnest doesn't return the whole array
contents at once, so it's just as capable of being optimized as any
single-purpose implementation. If you exit the loop early, you just
don't call it anymore.
regards, tom lane