Re: repack: clarify final phase of concurrent mode in file header comment

Chao Li <li.evan.chao@gmail.com>

From: Chao Li <li.evan.chao@gmail.com>
To: Jakub Wartak <jakub.wartak@enterprisedb.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>, Álvaro Herrera <alvherre@kurilemu.de>
Date: 2026-06-10T09:21:40Z
Lists: pgsql-hackers

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> On Jun 10, 2026, at 16:33, Jakub Wartak <jakub.wartak@enterprisedb.com> wrote:
> 
> On Thu, Apr 16, 2026 at 5:33 AM Chao Li <li.evan.chao@gmail.com> wrote:
>> 
>> Hi,
>> 
>> The file header comment in repack.c briefly explains the workflow of concurrent mode as:
>> 
>> 1. Lock the table with ShareUpdateExclusiveLock
>> 2. Do an initial copy as non-concurrent mode
>> 3. While the initial copy is going on, accumulates concurrent changes to a file
>> 4. After the initial copy, read the file and re-apply the changes
>> 5. Upgrade to AccessExclusiveLock and swap the relfilenodes
>> 
>> When I read the comment, I got confused at step 4. While that re-apply pass is running, concurrent changes can still occur, so what happens to those changes?
>> 
>> After reading the code, I see that there is actually an extra step after upgrading to AccessExclusiveLock to process the remaining changes.
>> 
>> I am afraid other readers may have the same confusion, so I am proposing this small patch to make the file header comment a bit clearer.
> 
> LGTM, so +1
> 
> -J.

Thanks for the review.

Rebased to v2.

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