Re: proposal: new polymorphic types - commontype and commontypearray

pá 13. 3. 2020 v 23:42 odesílatel Tom Lane <tgl@sss.pgh.pa.us> napsal:

> Pavel Stehule <pavel.stehule@gmail.com> writes:
> > [ anycompatible-types-20191127.patch ]
>
> I'm starting to review this patch seriously.  I've found some bugs and
> things I didn't like, and the documentation certainly needs work, but
> I think I can get it to a committable state before too much longer.
>
> What I want to talk about right now is some preliminary refactoring
> that I'd like to do, as shown in the 0001 patch below.  (0002 is the
> rest of the patch as I currently have it.)  There are two main things
> in it:
>
> 1. Rearrange the macros in pseudotypes.c so that we don't have any
> pure-boilerplate functions that aren't built by the macros.  I don't
> think this should be controversial, as it's not changing anything
> functionally.
>
> 2. Refactor the function signature validation logic in pg_proc.c and
> pg_aggregate.c to avoid having duplicate logic between those two.
> I did that by creating new functions in parse_coerce.c (for lack of
> a better place) that say whether a proposed result type or aggregate
> transition type is valid given a particular set of declared input types.
> The reason that this might be controversial is that it forces a slightly
> less precise error detail message to be issued, since the call site that's
> throwing the error doesn't know exactly which rule was being violated.
> (For example, before there was a specific error message about anyrange
> result requiring an anyrange input, and now there isn't.)
>
> I think this is all right, mainly because we'd probably end up with
> less-precise messages anyway for the more complex rules that 0002 is
> going to add.  If anybody's really hot about it, we could complicate
> the API, say by having the call sites pass in the primary error message
> or by having the checking subroutines pass back an errdetail string.
>
> We definitely need to do *something* about that, because it's already
> the case that pg_aggregate.c is out of step with pg_proc.c about
> polymorphism rules --- it's not enforcing the anyrange rule.  I think
> there's probably no user-reachable bug in that, because an aggregate
> is constrained by its implementation functions for which the rule
> would be enforced, but it still seems not good.
>

Unfortunately the error message " A function returning "anyrange" must have
at least one "anyrange" argument." will be missing.

This prerequisite is not intuitive. Second question is if we need special
rule for anyrange.

Regards

Pavel


> Thoughts?
>
>                         regards, tom lane
>
>