Re: Should "select 'nan'::float = 'nan'::float;" return false as per IEEE 754

On 28 October 2012 09:43, Hannu Krosing <hannu(at)2ndquadrant(dot)com> wrote:
> This is how PostgreSQL currently works -
>
> 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
>
> As per IEEE 754 a NaN behaves similar to NULL in SQL.

FWIW there is a note in the documentation about this:

"Note: IEEE754 specifies that NaN should not compare equal to any
other floating-point value (including NaN). In order to allow
floating-point values to be sorted and used in tree-based indexes,
PostgreSQL treats NaN values as equal, and greater than all non-NaN
values."