On Thu, Jun 22, 2023, at 07:51, Joel Jacobson wrote: > For instance, how should hashset_count() work? > > Given the query, > > SELECT hashset_count('{1,2,3,null}'::int4hashset); > > Should we, > > a) threat NULL as a distinct value and return 4? > > b) ignore NULL and return 3? > > c) return NULL? (since the presence of NULL can be thought to render > the entire count indeterminate) > > I think my personal preference is (b) since it is then consistent with > how COUNT() works.
Having thought a bit more on this matter, I think it's better to remove hashset_count() since the semantics are not obvious, and instead provide a hashset_cardinality() function, that would obviously include a possible null value in the number of elements: SELECT hashset_cardinality('{1,2,3,null}'::int4hashset); 4 SELECT hashset_cardinality('{null}'::int4hashset); 1 SELECT hashset_cardinality('{null,null}'::int4hashset); 1 SELECT hashset_cardinality('{}'::int4hashset); 0 SELECT hashset_cardinality(NULL::int4hashset); NULL Sounds good? /Joel