Re: comparing NEW and OLD (any good this way?)

On Wed, Jul 29, 2009 at 01:15:27PM +0000, Jasen Betts wrote:
> On 2009-07-23, Sam Mason <sam(at)samason(dot)me(dot)uk> wrote:
> > http://www.postgres.cz/index.php/PostgreSQL_SQL_Tricks#Attention_on_IS_NULL_and_IS_NOT_NULL_operators_for_composite_types
> >
> > is scary; even worse is that it was changed to be like this in 8.2
> > because the standard says it should behave this way. What on earth were
> > they thinking when they defined the standard this way?
>
> since any comparson involving those tuples will return NULL true is the
> correct value for IS NULL

I think you missed the point:

SELECT r IS NULL, r IS NOT NULL
FROM (VALUES (1,NULL)) r(a,b);

returns FALSE for *both* columns. How can a row be both NULL *and*
non-NULL?

> if you are bothered by this behavior you are misusing NULL.

I understand that this is the specified behavior, and hence PG is
correctly following the spec--but it still bothers me.

--
Sam http://samason.me.uk/