Date: Fri, 18 Jul 2025 18:49:12 +0900 (JST)
Message-Id: <20250718.184912.63592412993633060.kou@clear-code.com>
To: sawada.mshk@gmail.com
Cc: andres@anarazel.de, michael@paquier.xyz, david.g.johnston@gmail.com,
 tgl@sss.pgh.pa.us, zhjwpku@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 <CAD21AoAQkjU=o0nX4y0jtX0BnsrqA04g2ABqrUwjT88YeEWarA@mail.gmail.com>
  "Re: Make COPY format extendable: Extract COPY TO format implementations" on Thu, 17 Jul 2025 13:33:13 -0700,
  Masahiko Sawada <sawada.mshk@gmail.com> wrote:

>> I've not followed the development of this patch - but I continue to be
>> concerned about the performance impact it has as-is and the amount of COPY
>> performance improvements it forecloses.
>>
>> This seems to add yet another layer of indirection to a lot of hot functions
>> like CopyGetData() etc.
>>
> 
> The most refactoring works have been done by commit 7717f6300 and
> 2e4127b6d with a slight performance gain. At this stage, we're trying
> to introduce the registration API so that extensions can provide their
> callbacks to the core. Some functions required for I/O such as
> CopyGetData() and CopySendEndOfRow() would be exposed but I'm not
> going to add additional indirection function call layers.

I think Andres is talking about any indirection not only
indirection function call. In this case, "cstate->XXX" ->
"cstate->edata->XXX".

It's also mentioned in my e-mail. I'm not sure whether it
has performance impact but it's better that we benchmark to
confirm whether there is any performance impact or not with
the Copy{From,To}ExecutionData approach.


Thanks,
-- 
kou