Mihail Nikalayeu <[email protected]> wrote:

> > Indeed, the server log seems to indicate relationship to
> > VACUUM:
> > 2026-02-01 16:44:58.878 UTC autovacuum worker[22589] LOG:  automatic vacuum 
> > of table "postgres.pg_catalog.pg_class": index scans: 1
> 
> O, it's a good clue!
> 
> I have added some vacuum calls for pg_class in a stress test - and now it 
> fails much more often (check attachment).
> 
> It is "ERROR:  cache lookup failed for relation" - but I think it may share 
> the cause with "attempted to overwrite invisible tuple.

I've just reported one issue [1] that causes this, but that does not seem to
be related to the "attempted to overwrite invisible tuple" error.

> See:
> https://cirrus-ci.com/build/4852126532239360 - with "Use multiple snapshots 
> to copy the data."
> https://cirrus-ci.com/build/6429084491710464 - with "Use background worker to 
> do logical decoding."
> 
> But I am unable to reproduce the issue with only "Add CONCURRENTLY option to 
> REPACK command."
> https://cirrus-ci.com/build/6467070524653568

No idea why VACUUM makes the issue happen too often. Maybe it's related to the
PD_ALL_VISIBLE flage, but I've got no detailed explanation. I also don't know
why it does not reproduce w/o the logical decoding worker.

Thanks again for your testing!

[1] https://www.postgresql.org/message-id/61812.1770637345%40localhost

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com


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