Upgrade to PostgreSQL 14 in production

[jayaddison]

Is your feature request related to a problem? Please describe. This is an issue to track progress upgrading from PostgreSQL v13 to v14 in production.

Describe the solution you'd like Follow the guidance at https://www.postgresql.org/docs/14/upgrading.html

[jayaddison]

Notes:

• pg_upgrade seems to be an applicable strategy here
• In our hosting environment, PostgreSQL data is stored under /mnt/persistence/postgresql (as defined in #27)
• On Debian-based systems, symlinking is required for the postgresql.conf files (and conf.d directory that they reference) before running the upgrade this seems inaccurate -- it is true that both the old and new clusters require an appropriately-configured postgresql.conf file, but symlinks are not required to do that.
  • This was apparent from inspecting the output in pg_upgrade_server.log after an attempted upgrade
  • https://wiki.postgresql.org/wiki/Using_pg_upgrade_on_Ubuntu/Debian has some relevant guidance
• Applied configuration and performance tweaks from v13 postgresql.conf to v14 postgresql.conf before upgrade

Post-upgrade fixups:

• Applied database access rules from v13 pg_hba.conf to v14 pg_hba.conf

[jayaddison]

Upgrade complete. The backend product administration interface was accessed after the upgrade, and it rendered as expected, confirming that connectivity to the database is restored and functional.

[jayaddison]

(also performed some cleanup to remove postgresql-13-related Debian packages from the server host. data from the pre-upgrade v13 database has been retained, as with the upgrade from v12 to v13)

[jayaddison]

Some notes from a recent PostgreSQL 16 upgrade:

• Symlinks weren't strictly necessary, but it is important to use the correct data-directory configuration for both clusters.
• An example in the pg_upgrade manual mentions the --old-datadir and --new-datadir options -- they might appear at first glance to accept the persistence/storage directories -- but in fact they can (should?) be pointed to the old and new config directories. This is explained elsewhere in the manual already.