Re: WIP: Rework access method interface

Tom Lane wrote:
> Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> > Tom Lane wrote:
> >>> ... btw, what is the point of catalog/opfam_internal.h?
>
> > The whole point of splitting the struct declaration to a new header was
> > to get a DDL deparser to examine the list of objects being created, so
> > that it could construct the deparsed command. If the struct is opaque
> > to the outside world, there's no way to do that (as I recall, you can't
> > construct the full command starting from the parsed version only -- you
> > need access to the OIDs of the ops/procs actually added to the opclass.)
>
> Hm. OK, looking closer, I see that we've effectively exposed these
> structs as being what is passed to EventTriggerCollectCreateOpClass, so
> even if there's not currently any committed code that can read that info,
> we clearly need the structs to be accessible to interested event triggers.
> I'm not sold that that was a great design, but it's what's there.

All the deparsers are expected to be able to understand internal
representations of commands, though, such as OIDs and so on. If you
have a better idea (I don't), we can still rework the API we present to
deparser extensions.

> > That's a different argument, with which I don't necessarily disagree.
> > I think it's not unlikely that a verifier will want to examine the
> > contents of the struct, but I don't think that means we need to expose
> > the struct in amapi.h.
>
> I think we'd be considerably better off to *not* re-use OpFamilyMember
> in the verifier API. It's a struct that was only ever designed for
> internal use in CREATE/ALTER OPERATOR CLASS.
>
> I'm kind of inclined to just let the verifiers read the catalogs for
> themselves. AFAICS, a loop around the results of SearchSysCacheList
> is not going to be significantly more code than what this patch does,
> and it avoids presuming that we know what the verifiers will wish to
> look at.

Hmm, so this amounts to saying the verifier can only run after the
catalog rows are written. Is that okay?

--
Álvaro Herrera http://www.2ndQuadrant.com/
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