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

Hi,

In <CAD21AoB5x86TTyer90iSFivnSD8MFRU8V4ALzmQ=rQFw4QqiXQ(at)mail(dot)gmail(dot)com>
"Re: Make COPY format extendable: Extract COPY TO format implementations" on Mon, 15 Jan 2024 16:03:41 +0900,
Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:

>> Defining one more static const struct instead of providing a
>> convenient (but a bit tricky) macro may be straightforward:
>>
>> static const CopyToFormatRoutine testfmt_copyto_routine = {
>> .type = T_CopyToFormatRoutine,
>> .start_fn = testfmt_copyto_start,
>> .onerow_fn = testfmt_copyto_onerow,
>> .end_fn = testfmt_copyto_end
>> };
>>
>> static const CopyFormatRoutine testfmt_copyto_handler = {
>> .type = T_CopyFormatRoutine,
>> .is_from = false,
>> .routine = (Node *) &testfmt_copyto_routine
>> };
>
> Yeah, IIUC this is the option 2 you mentioned[1]. I think we can go
> with this idea as it's the simplest.
>
> [1] https://www.postgresql.org/message-id/20240110.120034.501385498034538233.kou%40clear-code.com

Ah, you're right. I forgot it...

> That is CopyFormatRoutine will be like:
>
> typedef struct CopyFormatRoutine
> {
> NodeTag type;
>
> /* either CopyToFormatRoutine or CopyFromFormatRoutine */
> Node *routine;
> } CopyFormatRoutine;
>
> And the core can check the node type of the 'routine7 in the
> CopyFormatRoutine returned by extensions.

It makes sense.

If no more comments about the current design, I'll start
implementing this feature based on the current design.

Thanks,
--
kou