min() and NaN

Hi,

I have a table containing a double precision column. That column
contains at least one judiciously placed NaN.

I'd expect the aggregate function min() to return the minimum, valid
numeric value. Instead, it seems to return the minimum value from the
subset of rows following the 'NaN'.

What's going here? What should I expect the aggregate function min() to
return in this case? And why?

Any help is appreciated,
Mike

testdb=> \d min_with_nan
Table "public.min_with_nan"
Column | Type | Modifiers
--------+------------------+-----------
col1 | double precision |

testdb=> select * from min_with_nan ;
col1
-------
3.141
2.718
NaN
10
(4 rows)

testdb=> select min(col1) from min_with_nan ;
min
-----
10
(1 row)

testdb=> select min(col1) from min_with_nan where col1 != 'NaN';
min
-------
2.718
(1 row)