The PostgreSQL 10.4 upgrade involves changes to some function markings (see release notes, E.1.2, second and third bullet points for specifics). One way to make these changes is to use `ALTER FUNCTION` to change the functions in your existing databases. While this was mainly straightforward, I'm unclear on whether the `template0` database must be changed in this manner or if it is automatically updated when the upgrade is applied. The documentation indicates that in general you shouldn't manually change the `template0` database.
If you ever go and CREATE DATABASE TEMPLATE template0 you will not get the correct markings unless you've updated template0 (w/o TEMPLATE template0 you pull from template1, probably want to update that as well).
Related question - the post-installation instructions that are part of the news releases seem like something that should be part of the release notes...but they are not.
