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.
this function should to have some distinguish name than other aggregates because important work of this func is not some calculation but some constraint check.
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.