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

2015-10-28 18:38 GMT+01:00 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:

> Marko Tiikkaja <marko(at)joh(dot)to> writes:
> > Here's a patch for the aggregate function outlined by Corey Huinker in
> > CADkLM=foA_oC_Ri23F9PbfLnfwXFbC3Lt8bBzRu3=CB77G9_qw(at)mail(dot)gmail(dot)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.
>
> regards, tom lane
>
>
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