Django migrations

Read these files first, before writing or editing a migration:

• docs/published/handbook/engineering/developing-locally.md (## Django migrations, ### Non-blocking migrations, ### Resolving merge conflicts)
• docs/published/handbook/engineering/safe-django-migrations.md
• docs/published/handbook/engineering/databases/schema-changes.md
• products/README.md (## Adding or moving backend models and migrations) when working in products/*

If the task is a ClickHouse migration, use clickhouse-migrations instead.

Workflow

1. Classify the change as additive (new nullable column, new table) or risky (drop/rename, NOT NULL, indexes, constraints, large data updates, model moves). A change is also risky if it touches a hot table, regardless of how additive it looks. See also the cross-language NOT NULL hazard below.
2. Generate: DEBUG=1 ./manage.py makemigrations [app_label]. For merge conflicts: python manage.py rebase_migration <app> && git add <app>/migrations (posthog or ee).
3. Apply safety rules from safe-django-migrations.md — the doc covers multi-phase rollouts, SeparateDatabaseAndState, concurrent operations, idempotency, and all risky patterns in detail.
4. Validate: ./manage.py sqlmigrate <app> <migration_number>, run tests, confirm linear migration sequence.