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

On Fri, Feb 28, 2025 at 1:58 PM Sutou Kouhei <kou(at)clear-code(dot)com> wrote:
>
> Hi,
>
> In <CAD21AoDr13=dx+k8gmQnR5_bY+NskyN4mbSWN0KhQncL6xuPMA(at)mail(dot)gmail(dot)com>
> "Re: Make COPY format extendable: Extract COPY TO format implementations" on Fri, 28 Feb 2025 11:50:39 -0800,
> Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> > I initially thought it would be acceptable to stop
> > NextCopyFromRawFields exposed since NextCopyFrom() could serve as an
> > alternative. For example, the NextCopyFromRawFields() function was
> > originally exposed in commit 8ddc05fb01ee2c primarily to support
> > extension modules like file_fdw but file_fdw wasn't utilizing this
> > API. I pushed the patch without the above change. Unfortunately, this
> > commit subsequently broke file_text_array_fdw[1] and made BF animal
> > crake unhappy[2].
> >
> > [1] https://github.com/adunstan/file_text_array_fdw
> > [2] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=crake&dt=2025-02-28%2018%3A47%3A02
>
> Thanks for the try!
>
> > Upon examining file_text_array_fdw more closely, I realized that
> > NextCopyFrom() may not be a suitable replacement for
> > NextCopyFromRawFields() in certain scenarios. Specifically,
> > NextCopyFrom() assumes that the caller has prior knowledge of the
> > source data's column count, making it inadequate for cases where
> > extensions like file_text_array_fdw need to construct an array of
> > source data with an unknown number of columns. In such situations,
> > NextCopyFromRawFields() proves to be more practical. Given these
> > considerations, I'm now leaning towards implementing the proposed
> > change. Thoughts?
>
> You suggest that we re-export NextCopyFromRawFields() (as a
> wrapper of static inline version) for backward
> compatibility, right? It makes sense. We should keep
> backward compatibility because there is a use-case of
> NextCopyFromRawFields().

Yes, I've submitted the patch to re-export that function[1]. Could you
review it?

Regards,

[1] https://www.postgresql.org/message-id/CAD21AoBA414Q76LthY65NJfWbjOxXn1bdFFsD_NBhT2wPUS1SQ%40mail.gmail.com

--
Masahiko Sawada
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