Date: Tue, 16 Jan 2024 11:53:00 +0900 (JST)
Message-Id: <20240116.115300.677614968695326715.kou@clear-code.com>
To: sawada.mshk@gmail.com
Cc: michael@paquier.xyz, zhjwpku@gmail.com, andrew@dunslane.net,
 nathandbossart@gmail.com, pgsql-hackers@postgresql.org
Subject: Re: Make COPY format extendable: Extract COPY TO format
 implementations
From: Sutou Kouhei <kou@clear-code.com>
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Hi,

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