| From: | shihao zhong <zhong950419(at)gmail(dot)com> |
|---|---|
| To: | greg(at)burd(dot)me |
| Cc: | boekewurm+postgres(at)gmail(dot)com, manuelreyesbravo(at)gmail(dot)com, hannuk(at)google(dot)com, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: UNDO with FILEOPS, and the FLUX table AM |
| Date: | 2026-11-10 03:56:46 |
| Message-ID: | CAGRkXqSGje6j0RgKLvgeB3L9vxo5B8p0GTLv2JC4-D0ammveFw@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hi Greg,
Thanks for v9,
I had a few thoughs here.
1. If a checkpoint comes after a transaction writes its undo, a crash
does not undo it. Replay starts at the redo point. CREATE
DATABASE can hit this.
2. A crash in the middle of CREATE DATABASE still seems to leave the
new directory behind. With wal_log the undo only calls rmdir().
That fails because the relation files are still inside. With file_copy
the cleanup is only kept in memory, so the crash loses it.
3. These commands cannot run in a transaction block, so the
subtransaction and 2PC code is never used. Could it wait for a user?
Thanks,
Shihao
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