Read DATABASE_ADAPTER variable from app when setting DATABASE_URL

README.md

@@ -129,3 +129,30 @@ dokku mysql:clone lolipop new_database
 # finally, you can destroy the container
 dokku mysql:destroy lolipop
 ```
+
+## Changing database adapter
+
+It's possible to change the protocol for DATABASE_URL by setting
+the environment variable DATABASE_ADAPTER on the app:
+
+```
+dokku config:set lolipop DATABASE_ADAPTER=mysql2
+dokku mysql:link lolipop playground
+```
+
+Will cause DATABASE_URL to be set as
+mysql2://mysql:SOME_PASSWORD@dokku-mysql-lolipop:3306/lolipop
+
+CAUTION: Changing DATABASE_ADAPTER after linking will cause dokku to believe
+the service is not linked when attempting to use `dokku mysql:unlink` or
+`dokku mysql:promote`.
+You should be able to fix this by
+
+- Changing DATABASE_URL manually to the new value.
+
+OR
+
+- Set DATABASE_ADAPTER back to its original setting
+- Unlink the service
+- Change DATABASE_ADAPTER to the desired setting
+- Relink the service