[Justin Pryzby <pryzby@telsasoft.com>]

I noticed this during beta1, but dismissed the issue when it wasn't easily
reproducible.  Now, I saw the same problem while upgrading from beta1 to beta2,
so couldn't dismiss it.  It turns out that LOs are lost if VACUUM FULL was run.

| /usr/pgsql-15b1/bin/initdb --no-sync -D pg15b1.dat -k
| /usr/pgsql-15b1/bin/postgres -D pg15b1.dat -c logging_collector=no -p 5678 -k /tmp&
| psql -h /tmp postgres -p 5678 -c '\lo_import /etc/shells' -c 'VACUUM FULL pg_largeobject'
| rm -fr pg15b2.dat && /usr/pgsql-15b2/bin/initdb --no-sync -k -D pg15b2.dat && /usr/pgsql-15b2/bin/pg_upgrade -d pg15b1.dat -D pg15b2.dat -b /usr/pgsql-15b1/bin
| /usr/pgsql-15b2/bin/postgres -D pg15b2.dat -c logging_collector=no -p 5678 -k /tmp&

Or, for your convenience, with paths in tmp_install:
| ./tmp_install/usr/local/pgsql/bin/initdb --no-sync -D pg15b1.dat -k
| ./tmp_install/usr/local/pgsql/bin/postgres -D pg15b1.dat -c logging_collector=no -p 5678 -k /tmp&
| psql -h /tmp postgres -p 5678 -c '\lo_import /etc/shells' -c 'VACUUM FULL pg_largeobject'
| rm -fr pg15b2.dat && ./tmp_install/usr/local/pgsql/bin/initdb --no-sync -k -D pg15b2.dat && ./tmp_install/usr/local/pgsql/bin/pg_upgrade -d pg15b1.dat -D pg15b2.dat -b ./tmp_install/usr/local/pgsql/bin
| ./tmp_install/usr/local/pgsql/bin/postgres -D pg15b2.dat -c logging_collector=no -p 5678 -k /tmp&

postgres=# table pg_largeobject_metadata ;
 16384 |       10 | 

postgres=# \lo_list 
 16384 | pryzbyj | 

postgres=# \lo_export 16384 /dev/stdout
lo_export
postgres=# table pg_largeobject;

postgres=# \dt+ pg_largeobject
 pg_catalog | pg_largeobject | table | pryzbyj | permanent   | heap          | 0 bytes | 

I reproduced the problem at 9a974cbcba but not its parent commit.

commit 9a974cbcba005256a19991203583a94b4f9a21a9
Author: Robert Haas <rhaas@postgresql.org>
Date:   Mon Jan 17 13:32:44 2022 -0500

    pg_upgrade: Preserve relfilenodes and tablespace OIDs.

-- 
Justin