On Thu, Jul 07, 2022 at 02:38:44PM -0400, Robert Haas wrote: > On Thu, Jul 7, 2022 at 2:24 PM Bruce Momjian <br...@momjian.us> wrote: > > On Thu, Jul 7, 2022 at 01:38:44PM -0400, Robert Haas wrote: > > > On Thu, Jul 7, 2022 at 1:10 PM Justin Pryzby <pry...@telsasoft.com> wrote: > > > > Maybe it's a good idea to check that the file is empty before > > > > unlinking... > > > > > > If we want to verify that there are no large objects in the cluster, > > > we could do that in check_new_cluster_is_empty(). However, even if > > > there aren't, the length of the file could still be more than 0, if > > > there were some large objects previously and then they were removed. > > > So it's not entirely obvious to me that we should refuse to remove a > > > non-empty file. > > > > Uh, that initdb-created pg_largeobject file should not have any data in > > it ever, as far as I know at that point in pg_upgrade. How would values > > have gotten in there? Via pg_dump? > > I was thinking if the user had done it manually before running pg_upgrade.
We're referring to the new cluster which should have been initdb'd more or less immediately before running pg_upgrade [0]. It'd be weird to me if someone were to initdb a new cluster, then create some large objects, and then maybe delete them, and then run pg_upgrade. Why wouldn't they do their work on the old cluster before upgrading, or on the new cluster afterwards ? Does anybody actually do anything significant between initdb and pg_upgrade ? Is that considered to be supported ? It seems like pg_upgrade could itself run initdb, with the correct options for locale, checksum, block size, etc (although it probably has to support the existing way to handle "compatible encodings"). Actually, I think check_new_cluster_is_empty() ought to prohibit doing work between initdb and pg_upgrade by checking that no objects have *ever* been created in the new cluster, by checking that NextOid == 16384. But I have a separate thread about "pg-upgrade allows itself to be re-run", and this has more to do with that than about whether to check that the file is empty before removing it. -- Justin
