There are only three breaking changes in this release, one of them is very significant, the other two are minor.
A new callback min_pg_version/0 has been added to the repo, but a default implementation is set up that reads the version from postgres directly, the first time it is required. It is cached until the repo is reinitialized, at which point it is looked up again.
While most things will work with versions as low as 9, we are relying on features of newer postgres versions and intend to do so more in the future. We will not be testing against versions lower than 14, and we will not be supporting them. If you are using an older version of postgres, you will need to upgrade.
If you must use an older version, the only thing that you'll need to change in the short term is to handle the fact that we now use gen_random_uuid() as the default for generated uuids (see below), which is only available after postgres 13. Additionally, if you are on postgres 12 or earlier, you will need to replace ANYCOMPATIBLE with ANYELEMENT in the ash-functions extension migration.
In the past, we used uuid_generate_v4() as the default for generated uuids. This function is part of the uuid-ossp extension, which is not installed by default in postgres. gen_random_uuid() is a built-in function that is available in all versions of postgres 13 and higher. If you are using an older version of postgres, you will need to install the uuid-ossp extension and change the default in your migrations.
This is a layer of safety to ensure consistency in the default values of a database and the datetimes that are sent to/from the database. When you generate migrations you will notice your timestamps change from defaulting to now() in your migrations to now() AT TIMESTAMP 'utc'. You are free to undo this change, by setting migration_defaults in your resource, or simply by deleting the generated migration.