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

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().

Thanks,
--
kou