How can i solve a migration issue in django project hosted on heroku?

Question

My project hosted on heroku and recently i want to change the size of one column in db but after running makemigrations command and then migrate command it gives an error and i don't want to lose my data .

   H:\shuboy2014>heroku run python manage.py makemigrations posts
   Running python manage.py makemigrations posts on shuboy2014... up, run.9067
   Migrations for 'posts':
     0003_auto_20160608_1404.py:
       - Alter field slug on post       

   H:\shuboy2014>heroku run python manage.py migrate
   Running python manage.py migrate on shuboy2014... up, run.3731
   Operations to perform:
     Apply all migrations: admin, contenttypes, posts, sessions, auth
   Running migrations:
     No migrations to apply.
     Your models have changes that are not yet reflected in a migration, and so won't be applied.
     Run 'manage.py makemigrations' to make new migrations, and then re-run 'manage.py migrate' to apply them.

Any helpful suggestions will be appreciable .

Answer 1

heroku run commands run on One-Off Dynos with an ephemeral file system, so you are generating the migrations files on a file system that is immediately destroyed.

You should generate migrations locally, committing and pushing them, and then executing the heroku run python manage.py migrate command.

Answer 2

I just run makemigrations and migrate command on my local computer and then push it on heroku and run both commands again and its done .

 H:\shuboy2014>heroku run python manage.py migrate
 Running python manage.py migrate on shuboy2014... up, run.6192
 Operations to perform:
   Apply all migrations: contenttypes, auth, posts, sessions, admin
 Running migrations:
   Rendering model states... DONE
   Applying posts.0003_auto_20160608_2001... OK