Re: [HACKERS] Re: [DOCS] Re: FE/BE protocol revision patch

>
> > Once atttypmod is exposed to applications it will be much harder to
> > change its representation or meaning
>
> Yeah, that is what I'm worried about too...
>
> - Tom (the other "tgl")

Well, atttypmod is stored in various C structures, like Resdom, so we
would need some C representation for the type, even it is just a void *.

Very few system columns are varlena/text, and for good reason, perhaps.

Such a change is certainly going to make things in the backend slightly
harder, so please let me what advantage a varlena atttypmod is going to
have.

Zero overhead for types that don't use it is meaningless, because the
varlena length is 4 bytes, while current atttypmod is only two. Second,
I don't see how a varlena makes atttypmod less type-specific. We
currently return a -1 when it is not being used.

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