2010/11/18 Tom Lane <tgl@sss.pgh.pa.us>:
> 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.
no it isn't - actually you cannot to limit a returned set when you
call SRF function in expression context - if I remember well. We can
change it - but this is other complexity.
Pavel
>
> regards, tom lane
>