Re: Make COPY format extendable: Extract COPY TO format implementations

Hi,

In <20250714(dot)173803(dot)865595983884510428(dot)kou(at)clear-code(dot)com>
"Re: Make COPY format extendable: Extract COPY TO format implementations" on Mon, 14 Jul 2025 17:38:03 +0900 (JST),
Sutou Kouhei <kou(at)clear-code(dot)com> wrote:

>> I've reviewed the 0001 and 0002 patches. The API implemented in the
>> 0002 patch looks good to me, but I'm concerned about the capsulation
>> of copy state data. With the v42 patches, we pass the whole
>> CopyToStateData to the extension codes, but most of the fields in
>> CopyToStateData are internal working state data that shouldn't be
>> exposed to extensions. I think we need to sort out which fields are
>> exposed or not. That way, it would be safer and we would be able to
>> avoid exposing copyto_internal.h and extensions would not need to
>> include copyfrom_internal.h.

> In general, I agree that we should export only needed
> information.
>
> How about adding accessors instead of splitting
> Copy{From,To}State to Copy{From,To}ExecutionData? If we use
> the accessors approach, we can export only needed
> information step by step without breaking ABI.

Another idea: We'll add Copy{From,To}State::opaque
eventually. (For example, the v40-0003 patch includes it.)

How about using it to hide fields only for built-in formats?

Thanks,
--
kou