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
Attachments
- v2-0001-repack-clarify-final-phase-of-concurrent-mode-in-.patch (application/octet-stream) patch v2-0001
> 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/