Re: speedup COPY TO for partitioned table.

> On Oct 10, 2025, at 10:54, jian he <jian(dot)universality(at)gmail(dot)com> wrote:
>
>> 5
>> ```
>> +static void
>> +CopyRelTo(CopyToState cstate, Relation rel, Relation root_rel,
>> + uint64 *processed)
>> ```
>>
>> Instead of using a pointer to pass out processed count, I think it’s better to return the process count. I understand the current implementation allows continuous increment while calling this function in a loop. However, it’s a bit error-prone, a caller must make sure “processed” is well initialized. With returning a unit64, the caller’s code is still simple:
>>
>> ```
>> processed += CopyRelTo(cstate, …);
>> ```
>>
>> pgstat_progress_update_param was within CopyRelTo.
>> so we have to pass (uint64 *processed) to CopyRelTo.
>> Am I missing something?
>>
>>
>> Make sense. I didn’t notice postage_progress_update_param. So, “processed” is both input and output. In that case, I think the comment for parameter “processed” should be enhanced, for example:
>>
> if your function is:
>
> static processed CopyRelationTo(CopyToState cstate, Relation rel,
> Relation root_rel, uint64 *processed);
>
> where function return value is also passed as function argument,
> I think it will lead to more confusion.

I am not suggesting add a return value to the function. My comment was just to enhance the parameter comment of “processed”.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/