Re: Domains and arrays and composites, oh my

Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com> writes:
> On 09/28/2017 01:02 PM, Tom Lane wrote:
>>> I do think that treating a function returning a domain-over-composite
>>> differently from one returning a base composite is a POLA. We'd be very
>>> hard put to explain the reasons for it to an end user.

>> Do you have any thoughts about how we ought to resolve that?

> Not offhand. Maybe we need to revisit the decision not to modify the
> executor at all.

I think it's more of a parse analysis change: the issue is whether to
smash a function's result type to base when determining whether it emits
columns. Maybe we could just do that in that context, and otherwise leave
domains alone.

> One thought I had was that we could invent a new return
> type of TYPEFUNC_DOMAIN_COMPOSITE so there would be less danger of a PL
> just treating it as an unconstrained base type as it might do if it saw
> TYPEFUNC_COMPOSITE.

Hmm. That would be a way of forcing the issue, no doubt ...

regards, tom lane