Rails: PG::InsufficientPrivilege: ERROR: permission denied for relation schema_migrations

I had same issue and I solved by adding "Superuser" to the role.

First, list users and their privileges. If you followed above commands, root user does not have "Superuser" Attributes.

postgres=# \du
                                   List of roles
 Role name |                         Attributes                         | Member of
-----------+------------------------------------------------------------+-----------
 other     | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
 root      |                                                            | {}

Next, upgrade root to be a "Superuser".

postgres=# ALTER USER root WITH SUPERUSER;
ALTER ROLE

Again, list users and their privileges. Now root has "Superuser".

postgres=# \du
                               List of roles
 Role name |                         Attributes                         | Member of
-----------+------------------------------------------------------------+-----------
 other     | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
 root      | Superuser                                                  | {}

Hope it helps.

I guess you missed create password for your user. Try to create password as following:

CREATE USER root WITH PASSWORD 'your_new_password';
CREATE DATABASE svp-chicago_development;
GRANT ALL PRIVILEGES ON DATABASE svp-chicago_development to root;
ALTER DATABASE svp-chicago_development OWNER TO root;

Also, if you're using a service like Heroku, it's worth checking to see if you have overrun your row limit and write access has been revoked in the database.

You can do that by going to the dashboard, click on the app, click on the postgres service icon, then check the row limit.