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

Hi,

In <Zea4wXxpYaX64e_p(at)paquier(dot)xyz>
"Re: Make COPY format extendable: Extract COPY TO format implementations" on Tue, 5 Mar 2024 15:16:33 +0900,
Michael Paquier <michael(at)paquier(dot)xyz> wrote:

> CopyOneRowTo() could do something like that to avoid the extra
> indentation:
> if (cstate->routine)
> {
> cstate->routine->CopyToOneRow(cstate, slot);
> MemoryContextSwitchTo(oldcontext);
> return;
> }

OK. The v17 patch uses this style. Others are same as the
v16.

> I didn't know this trick. That's indeed nice.. I may use that for
> other stuff to make patches more presentable to the eyes. And that's
> available as well with `git diff`.

:-)

> If we basically agree about this part, how would the rest work out
> with this set of APIs and the possibility to plug in a custom value
> for FORMAT to do a pg_proc lookup, including an example of how these
> APIs can be used?

I'll send the following patches after this patch is
merged. They are based on the v6 patch[1]:

1. Add copy_handler
* This also adds a pg_proc lookup for custom FORMAT
* This also adds a test for copy_handler
2. Export CopyToStateData
* We need it to implement custom copy TO handler
3. Add needed APIs to implement custom copy TO handler
* Add CopyToStateData::opaque
* Export CopySendEndOfRow()
4. Export CopyFromStateData
* We need it to implement custom copy FROM handler
5. Add needed APIs to implement custom copy FROM handler
* Add CopyFromStateData::opaque
* Export CopyReadBinaryData()

[1] https://www.postgresql.org/message-id/flat/20240124.144936.67229716500876806.kou%40clear-code.com#f1ad092fc5e81fe38d3c376559efd52c

Thanks,
--
kou