Subject: Rework SLRU I/O errors handle

From: Maxim Orlov <[email-masked]>
Date: Thu, 26 Feb 2026 17:26:05 +0300

Hi!

Beginning of the discussion is here [0].

Historically, the SLRU module was designed to handle 32-bit
transactions. However, it is now utilised for handling a variety of
object types, like TransactionId, MultixactId, MultiXactOffset,
QueuePosition, and so on. But the IO error reporting system is still
designed to support 32-bit XIDs exclusively.

The proposed patchset allows us to define a "custom" callback to
improve error messages.

The first two commits add a callback and test case. The subsequent ones
improve I/O error messages. The last one adds the XID epoch to the error
message. It's purely optional, but I think it would be useful.

[0]
https://www.postgresql.org/message-id/CACG%3Dezbwy1zargXDNPeYXxZwRW3jXu_aD%3DrcG-7dc4fw7Y9Ojw%40mail.gmail.com

-- 
Best regards,
Maxim Orlov.

---

From: Heikki Linnakangas <[email-masked]>
Date: Fri, 6 Mar 2026 16:43:24 +0200

On 26/02/2026 16:26, Maxim Orlov wrote:
> [0] https://www.postgresql.org/message-id/ 
> CACG%3Dezbwy1zargXDNPeYXxZwRW3jXu_aD%3DrcG-7dc4fw7Y9Ojw%40mail.gmail.com 
> <https://www.postgresql.org/message-id/ 
> CACG%3Dezbwy1zargXDNPeYXxZwRW3jXu_aD%3DrcG-7dc4fw7Y9Ojw%40mail.gmail.com>

Thanks, looks reasonable.

I'm -1 on the last patch, "Expand xact SLRU IO-error to show epoch" 
though. The epoch isn't used in addressing the SLRU, the patch just 
expands the 32-bit XID into a full 64-bit XID using the current epoch. 
That seems misleading.

- Heikki