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

On Wed, Dec 6, 2023 at 3:28 PM Sutou Kouhei <kou@clear-code.com> wrote:
>
> Hi,
>
> In <CAEG8a3K9dE2gt3+K+h=DwTqMenR84aeYuYS+cty3SR3LAeDBAQ@mail.gmail.com>
>   "Re: Make COPY format extendable: Extract COPY TO format implementations" on Wed, 6 Dec 2023 15:11:34 +0800,
>   Junwang Zhao <zhjwpku@gmail.com> wrote:
>
> > For the extra curly braces, I mean the following code block in
> > CopyToFormatBinaryStart:
> >
> > + {        <-- I thought this is useless?
> > + /* Generate header for a binary copy */
> > + int32 tmp;
> > +
> > + /* Signature */
> > + CopySendData(cstate, BinarySignature, 11);
> > + /* Flags field */
> > + tmp = 0;
> > + CopySendInt32(cstate, tmp);
> > + /* No header extension */
> > + tmp = 0;
> > + CopySendInt32(cstate, tmp);
> > + }
>
> Oh, I see. I've removed and attach the v3 patch. In general,
> I don't change variable name and so on in this patch. I just
> move codes in this patch. But I also removed the "tmp"
> variable for this case because I think that the name isn't
> suitable for larger scope. (I think that "tmp" is acceptable
> in a small scope like the above code.)
>
> New code:
>
> /* Generate header for a binary copy */
> /* Signature */
> CopySendData(cstate, BinarySignature, 11);
> /* Flags field */
> CopySendInt32(cstate, 0);
> /* No header extension */
> CopySendInt32(cstate, 0);
>
>
> Thanks,
> --
> kou

Hi Kou,

I read the thread[1] you posted and I think Andres's suggestion sounds great.

Should we extract both *copy to* and *copy from* for the first step, in that
case we can add the pg_copy_handler catalog smoothly later.

Attached V4 adds 'extract copy from' and it passed the cirrus ci,
please take a look.

I added a hook *copy_from_end* but this might be removed later if not used.

[1]: https://www.postgresql.org/message-id/20180211211235.5x3jywe5z3lkgcsr%40alap3.anarazel.de
--
Regards
Junwang Zhao