Re: Nulls, arrays, records, IS NULL, IS DISTINCT FROM - Mailing list pgsql-hackers

David Fetter <david@fetter.org> writes:
> On Fri, Sep 29, 2006 at 12:53:19PM -0400, Tom Lane wrote:
>> In particular, the spec says
>>    ROW(1,2,NULL) IS NOT NULL
>> is false, because the row fields must be *all* not null to make it true.

> That's odd because as I understand the above,
>     ROW(1,2,NULL) IS NULL
> is also false.  Have I misunderstood?

Yup, they are both false.  The spec goes to some trouble to make it
clear that IS NULL/IS NOT NULL are not inverses for row values:
           NOTE 135 - For all R, "R IS NOT NULL" has the same result as           "NOT R IS NULL" if and only if R is
ofdegree 1. Table 16,           "<null predicate> semantics", specifies this behavior.
 

What I find odd is the lack of comparable language about arrays.
        regards, tom lane