Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Well, my 2 cents is that though we consider NULL when ordering via ORDER
> BY, we ignore it in MAX because it really isn't a value, and NaN seems
> to be similar to NULL.
Good idea, but I don't think we can get away with it. The spec says
that MAX/MIN have to be consistent with the comparison operators (and
therefore with ORDER BY):
iii) If MAX or MIN is specified, then the result is respec- tively the maximum or minimum
valuein TXA. These results are determined using the comparison rules specified in
Subclause8.2, "<comparison predicate>".
NULL can be special, because it acts specially in comparisons anyway.
But NaN is just a value of the datatype.
I'd be willing to go against the spec if I thought that having
ignore-NaNs behavior was sufficiently important, but I don't think it's
important enough to disregard the spec...
regards, tom lane
