bluedenim / vmigration-helper

Helpers for working with Django migrations

Van's Migration Helper

Django commands to help with running Django migrations.

Installation

• Add the dependency to your environment:

  pip install vmigration-helper
  

• Add the app vmgration_helper.apps.VMigrationHelperConfig to your list of installed apps in your settings:

  INSTALLED_APPS = [
    ...
    'vmigration_helper.apps.VMigrationHelperConfig',
    ...
  ]
  

Commands

migration_records

Shows existing migration records in your django_migration table.

Optional parameters:

• --format (console | csv) print the info in CSV or friendlier console format (default)

> python manage.py migration_records --format csv
ID,Applied,App,Name
175,2021-06-13T20:41:28.683900+00:00,contenttypes,0001_initial
176,2021-06-13T20:41:28.717886+00:00,auth,0001_initial
177,2021-06-13T20:41:28.742930+00:00,admin,0001_initial
178,2021-06-13T20:41:28.761938+00:00,admin,0002_logentry_remove_auto_add
179,2021-06-13T20:41:28.770319+00:00,admin,0003_logentry_add_action_flag_choices
180,2021-06-13T20:41:28.791287+00:00,contenttypes,0002_remove_content_type_name
...
192,2021-06-13T20:41:28.991814+00:00,sessions,0001_initial

These are the records of migrations applied. The fields indicate:

• ID - the ID of the record
• Applied - when the migration was applied
• App - name of the Django app
• Name - name of the migration

migration_current_id

Shows the ID of the latest migration record in your django_migration table.

> python manage.py migration_current_id
192

192 is the ID of the latest record as shown above.

migration_rollback

Roll-back (unapply) previously applied migrations after (but not including) the migration ID provided.

> python manage.py migration_rollback 176

The above will rollback migrations after 0001_initial of the auth app:

python manage.py migrate sessions zero
Operations to perform:
  Unapply all migrations: sessions
Running migrations:
  Rendering model states... DONE
  Unapplying sessions.0001_initial... OK

python manage.py migrate auth 0001_initial
Operations to perform:
  Target specific migration: 0001_initial, from auth
Running migrations:
  Rendering model states... DONE
  Unapplying auth.0012_alter_user_first_name_max_length... OK
  Unapplying auth.0011_update_proxy_permissions... OK
  Unapplying auth.0010_alter_group_name_max_length... OK
  Unapplying auth.0009_alter_user_last_name_max_length... OK
  Unapplying auth.0008_alter_user_username_max_length... OK
  Unapplying auth.0007_alter_validators_add_error_messages... OK
  Unapplying auth.0006_require_contenttypes_0002... OK
  Unapplying auth.0005_alter_user_last_login_null... OK
  Unapplying auth.0004_alter_user_username_opts... OK
  Unapplying auth.0003_alter_user_email_max_length... OK
  Unapplying auth.0002_alter_permission_name_max_length... OK

python manage.py migrate contenttypes 0001_initial
Operations to perform:
  Target specific migration: 0001_initial, from contenttypes
Running migrations:
  Rendering model states... DONE
  Unapplying contenttypes.0002_remove_content_type_name... OK

python manage.py migrate admin zero
Operations to perform:
  Unapply all migrations: admin
Running migrations:
  Rendering model states... DONE
  Unapplying admin.0003_logentry_add_action_flag_choices... OK
  Unapplying admin.0002_logentry_remove_auto_add... OK
  Unapplying admin.0001_initial... OK

Optional parameters:

• --dry-run will print the commands but will not actually run them

• --migrate-cmd <command to run migrations> sets the command to run migrations with. The command must accept the app and migration name as the {app} and {name} placeholders, respectively.

  For example:

  --migrate-cmd "pipenv run python manage.py migrate {app} {name}" 
  

  can be used to have the command run migrations using pipenv.

  For example:

  > pipenv run python manage.py migration_rollback 0 --dry-run --migrate-cmd "pipenv run python manage.py migrate {app} {name}"
  pipenv run python manage.py migrate sessions zero
  pipenv run python manage.py migrate auth 0001_initial
  pipenv run python manage.py migrate contenttypes 0001_initial
  pipenv run python manage.py migrate admin zero
  pipenv run python manage.py migrate auth zero
  pipenv run python manage.py migrate contenttypes zero
  

migration_delete

Deletes an entry from Django's migration records. This command should be used only as a last resort to fix up migration records that cannot be rolled back. No migration up/down is performed; the record is simply removed from django_migrations.

NOTE also that migrations that depend on the record being deleted will be "broken" after the deletion, so this command should only be run on "leaf" migration records unless you plan to also delete other migration records that depend on the one being deleted.

python manage.py migration_delete myapp 0003_some_migration
Confirm deletion of myapp:0003_some_migration (yes or no): yes

The command above deletes the migration 0003_some_migration for the app myapp (after getting confirmation).

To delete without confirmation, use the --yes option:

python manage.py migration_delete myapp 0003_some_migration --yes

Optional parameters:

• --yes will proceed to deleting the record without asking for confirmation

Ideas for automation

Here's an idea for automating the deployment of your Django app using these utilities:

• Deploy new code
• Run migration_current_id and capture the current ID
• Run migration normally
• Run your automated tests normally
  • If tests pass, you're done!
  • If tests fail, and you need to rollback, run migration_rollback <captured ID>