Understanding Database Migration Conflicts in Django

Django’s ORM migration system allows schema evolution, but incorrect migration sequences, missing dependencies, and manual schema changes can result in data integrity issues and migration failures.

Common Causes of Migration Conflicts

  • Manual schema changes: Database altered outside of Django’s migration system.
  • Conflicting migration files: Multiple branches modifying the same model field.
  • Out-of-sync migrations: Unapplied or missing migration files.
  • Historical migrations corruption: Deleting or modifying old migration files incorrectly.

Diagnosing Django Migration Issues

Checking Migration Status

List unapplied migrations:

python manage.py showmigrations --list

Inspecting Migration Dependencies

View migration history to detect inconsistencies:

python manage.py dbshell -c "SELECT * FROM django_migrations ORDER BY applied;"

Detecting Schema Drift

Compare model state with the database schema:

python manage.py makemigrations --check

Verifying Duplicate or Conflicting Migrations

Identify conflicting migration files:

ls -lh myapp/migrations/

Fixing Django Database Migration Issues

Reapplying Migrations

Reset migrations and apply them cleanly:

python manage.py migrate myapp zero
python manage.py makemigrations
python manage.py migrate

Manually Resolving Conflicts

Delete unnecessary migration files and recreate:

rm myapp/migrations/000*_conflict_migration.py
python manage.py makemigrations --merge

Correcting Historical Migration State

Fake apply migrations to match schema:

python manage.py migrate --fake myapp

Preventing Schema Drift

Ensure database and Django models stay synchronized:

python manage.py inspectdb

Preventing Future Migration Conflicts

  • Always generate migrations before modifying models in multiple branches.
  • Use makemigrations --merge to resolve conflicts when multiple developers work on migrations.
  • Avoid modifying old migration files unless necessary.
  • Regularly check migration history to ensure consistency.

Conclusion

Django migration conflicts arise from schema drift, manual database changes, or inconsistent migration files. By structuring migration workflows correctly, reapplying migrations cleanly, and preventing historical corruption, developers can maintain a stable database schema.

FAQs

1. Why do Django migrations fail?

Possible reasons include conflicting migration files, missing dependencies, or manual database schema modifications.

2. How do I fix migration conflicts in Django?

Use makemigrations --merge to resolve conflicts or reset migrations by rolling back to zero and reapplying.

3. What is schema drift in Django?

Schema drift occurs when the actual database schema differs from Django’s migration history, often caused by manual changes.

4. How do I prevent duplicate migrations?

Ensure that each model change has a corresponding migration and avoid modifying migrations manually.

5. Can I delete old migration files?

Yes, but only after squashing migrations or ensuring the database schema is consistent with the latest migration state.