Re: onlyvalue aggregate (was: First Aggregate Funtion?)

Marko Tiikkaja <marko@joh.to> writes:
> Here's a patch for the aggregate function outlined by Corey Huinker in 
> CADkLM=foA_oC_Ri23F9PbfLnfwXFbC3Lt8bBzRu3=CB77G9_qw@mail.gmail.com .  I 
> called it "onlyvalue", which is a horrible name, but I have nothing 
> better to offer.  (Corey called it "only", but that doesn't really work 
> since ONLY is a fully reserved keyword.)

On the name front, maybe think "single" rather than "only"?  This might
lead to "single()" or "single_value()", or "singleton()" if you want to
sound highbrow.

On the semantics front, I'm not sure that I like excluding nulls from the
input domain.  I'd rather that it acted like IS NOT DISTINCT, ie, nulls
are fine as long as all the input values are nulls.  The implementation
would need some work for that.
        regards, tom lane