If you're upgrading from a pre-release version, there will be a major Postgresql
version upgrade -- this should happen automatically, but **please take a
backup**, at least of the `<stack_name>_db` volume, if not all the data volumes,
before the upgrade. 

If you haven't taken a backup already, it's probably safest to bail using
Ctrl+C, take the backup, and re-run your `upgrade` / `deploy` command.