Andrew Dunstan <andrew@dunslane.net> writes:
> Yes, Multisets (a.k.a. bags and a large number of other names) would be
> interesting. But I wouldn't like to abandon pure sets either. Maybe a
> typmod indicating the allowed multiplicity of the type?
I don't think trying to use typmod to carry fundamental semantic
information will work, because we drop it in too many places
(e.g. there's no way to pass it through a function). If you want
both sets and multisets, they'll need to be two different container
types, even if code is shared under the hood.
regards, tom lane
