On Tue, Jul 11, 2017 at 12:44:33PM -0400, Tom Lane wrote:
> Over in
> https://www.postgresql.org/message-id/877ezgyn60....@metapensiero.it
> there's a gripe about array_agg() not working for a domain type.
> It fails because we don't create an array type over a domain type,
> so the parser can't identify a suitable output type for the polymorphic
> aggregate.
> We could imagine tweaking the polymorphic-function resolution rules
> so that a domain matched to ANYELEMENT is smashed to its base type,
> allowing ANYARRAY to be resolved as the base type's array type.
> While that would be a pretty localized fix, it seems like a kluge
> to me.
> Probably a better answer is to start supporting arrays over domain
> types.  That was left unimplemented in the original domains patch,
> but AFAICS not for any better reason than lack of round tuits.
> I did find an argument here:
> https://www.postgresql.org/message-id/3c98f7f6.29fe1...@redhat.com
> that the SQL spec forbids domains over arrays, but that's the opposite
> case (and a restriction we long since ignored, anyway).
> Can anyone think of a reason not to pursue that?

+1 for pursuing it.  When operations just compose, users get a more
fun experience.

David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david(dot)fetter(at)gmail(dot)com

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