Re: Multixid SLRU truncation bugs at wraparound

> On 6 Jan 2026, at 16:53, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
>
> For all branches, I propose v1-0002-Add-check-for-invalid-offset-at-multixid-truncati.patch to add a check for
oldestOffset== 0. That fixes the potential for catastrophic truncation with invalid offset 0. 

Multixid that is used in heap is WAL-logged. WAL-logged multixact has non-zero offset.
So in non-corrupted database such as condition is impossible.
However, I observed several incidents when AI recommended pg_resetwal to users.
Proposed safeguard might be useful to prevent sprawling corruption in database.



> On 6 Jan 2026, at 16:53, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
>
> But for 'master', I propose the attached v1-0001-Remove-some-unnecessary-code-from-multixact-trunc.patch.

The patch simplifies the code while maintaining correctness.
The only issue I can think of is that clog, commit_ts and async are still using approach based on SlruScanDirectory().


Best regards, Andrey Borodin.