Re: [HACKERS] [PATCH] Generic type subscripting

On Wed, Dec 09, 2020 at 12:49:48PM -0500, Tom Lane wrote:
> I've pushed the core patch now. The jsonb parts now have to be
> rebased onto this design, which I'm assuming Dmitry will tackle
> (I do not intend to). It's not quite clear to me whether we have
> a meeting of the minds on what the jsonb functionality should be,
> anyway. Alexander seemed to be thinking about offering an option
> to let the subscript be a jsonpath, but how would we distinguish
> that from a plain-text field name?
>
> BTW, while reviewing the thread to write the commit message,
> I was reminded of my concerns around the "is it a container"
> business. As things stand, if type A has a typelem link to
> type B, then the system supposes that A contains B physically;
> this has implications for what's allowed in DDL, for example
> (cf find_composite_type_dependencies() and other places).
> We now have a feature whereby subscripting can yield a type
> that is not contained in the source type in that sense.
> I'd be happier if the "container" terminology were reserved for
> that sort of physical containment, which means that I think a lot
> of the commentary around SubscriptingRef is misleading. But I do
> not have a better word to suggest offhand. Thoughts?

Would this be something more along the lines of a "dependent type," or
is that adding too much baggage?

Best,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778

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