Hello, I would like to ask a few questions about pg_upgrade when using --link option to avoid copying data files. 1. After running pg_upgrade but before starting new cluster, is it 100% safe to abort and go back to using the old cluster? For example: /usr/PostgreSQL/15/bin/pg_upgrade --link \ --old-datadir "/data/pgdb" \ --new-datadir "/data/pgdb.new" \ --old-bindir "/usr/PostgreSQL/9.6/bin" \ --new-bindir "/usr/PostgreSQL/15/bin" Upgrade succeeds but before I start the new cluster, I change my mind and want to revert to using the old cluster. Can I simply revert to using PostgreSQL 9.6 with these commands: rm -rf /data/pgdb.new mv /data/pgdb/global/pg_control.old /data/pgdb/global/pg_control Am I correct in thinking that apart from pg_control file, "pg_upgrade --link" does not modify the old cluster files in any incompatible ways? 2. Older pg_upgrade binary did not support --jobs argument. When upgrading from such older clusters, running the latest "pg_upgrade --jobs=N" fails at the very start. Is this expected? 3. I'm a bit confused about the correct procedure when it comes to upgrading primary and standby clusters. Looking at https://www.postgresql.org/docs/current/pgupgrade.html it mentions the following: "If you are upgrading standby servers using methods outlined in section Step 11, verify that the old standby servers are caught up by running pg_controldata against the old primary and standby clusters. Verify that the “Latest checkpoint location” values match in all clusters. (There will be a mismatch if old standby servers were shut down before the old primary or if the old standby servers are still running.) Also, make sure wal_level is not set to minimal in the postgresql.conf file on the new primary cluster." Does this mean pg_upgrade will not work on standby if it is out of sync with the primary? The page also talks about using rsync to copy data from primary to standby server. I would like to avoid doing large data copy. Are these upgrade steps likely to work: a) Disable replication temporary. b) Stop standby server and run pg_upgrade. c) Stop primary server and run pg_upgrade. d) Enable replication and start primary and standby and allow them to synchronize their data. Thanks.
