| From: | Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Andres Freund <andres(at)anarazel(dot)de>, scott(at)scottray(dot)io |
| Subject: | Re: Snapshot export on a standby corrupts hint bits on subxact overflow |
| Date: | 2026-07-29 09:36:06 |
| Message-ID: | amnJhkudengxKX+Y@bdtpg |
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| Thread: | |
| Lists: | pgsql-hackers |
Hi,
On Tue, Jul 28, 2026 at 06:07:34AM +0000, Bertrand Drouvot wrote:
> So, I think filtering is appropriate in both places:
>
> 1/ In ExportSnapshot(), do not include recovery subxip entries and committed
> child XIDs at or above xmax when counting and serializing them, so unnecessary
> entries do not consume the limited recovery subxip capacity.
>
> 2/ In pg_current_snapshot(), do not include source XIDs outside [xmin, xmax),
> so that it enforces the rule regardless of how the source snapshot was produced.
>
Following our off-list discussion, PFA v2 that addresses the comments above.
It adds xmax filtering, updates the documentation, and adds a few tests.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
| Attachment | Content-Type | Size |
|---|---|---|
| v2-0001-Don-t-discard-subxip-when-exporting-a-snapshot-ta.patch | text/x-diff | 18.1 KB |
| v2-0002-Read-the-in-progress-set-from-subxip-in-pg_curren.patch | text/x-diff | 11.0 KB |
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