Re: Optimizing maximum/minimum queries (yet again)

On Fri, Apr 08, 2005 at 23:40:28 -0400,
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Bruno Wolff III <bruno(at)wolff(dot)to> writes:
> > It should be possible to make this work for bool_and and bool_or as those
> > are equivalent to min and max for the boolean type.
>
> This would just be a matter of marking them properly in the catalogs.
>
> However, are they really equivalent in the corner cases? In particular,
> I think boolean AND across zero input rows is probably supposed to
> return TRUE, not NULL.

I am not sure what the spec says, but according to how the seem to work,
the answer appears to be that they are equivalent.

area=> select bool_and(true) where false;
bool_and
----------

(1 row)

area=> select bool_or(true) where false;
bool_or
---------

(1 row)