On 28 October 2012 09:43, Hannu Krosing <hannu@2ndquadrant.com> wrote:
> test=# select 'NaN'::float = 'NaN'::float as must_be_false;
> must_be_false
> ----------
> t
> (1 row)
>
> I think that PostgreSQL's behaviour of comparing two
> NaN-s as equal is wrong and Iwe should follow the IEEE 754 spec here
The reason that PostgreSQL does this is that in order for float to be
a btree indexable type, its semantics must follow the reflexive law.
This and other requirements of btree operator classes are described
under src/backend/access/nbtree/README.
--
Peter Geoghegan http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training and Services