> In my experience vacuumlo,
https://www.postgresql.org/docs/12/vacuumlo.html, is needed to remove
large objects, before vacuum can remove them from pg_largeobject.
Thanks for the suggestion! vacuumlo deletes any orphaned large objects,
presumably by using lo_unlink. While we don't use vacuumlo, our service
does clean up orphaned large objects in a similar way. And indeed,
inspecting the database reveals that there are no orphaned large objects.
Regards,
Jim Hurne