migration-safety-checkerlisted

# Migration Safety Checker Validates Django migrations are production-safe before they cause data loss. ## Activation Triggers This skill activates when: - Running `makemigrations` - Modifying model fields - Mentioning "migration", "schema", "alter table" - Adding/removing/renaming fields - Changing field types - Creating or modifying migration files ## Safety Requirements All migrations MUST be: - ✅ **Reversible** - Can roll back safely - ✅ **No data loss** - Preserve existing data - ✅ **Tested** - Run on staging first - ✅ **Safe for production** - No downtime operations - ✅ **Documented** - Explain what changes and why ## High-Risk Operations These operations require special attention: ### 🔴 CRITICAL RISK - Data Loss Possible 1. **Dropping columns** without data migration 2. **Renaming fields** without data migration 3. **Changing field types** (data conversion issues) 4. **Adding non-nullable fields** without default 5. **Removing tables** with data ### 🟡 MEDIUM RISK - Requires Careful Planning 1. **Adding indexes** on large tables (use `CONCURRENTLY`) 2. **Adding unique constraints** (check for duplicates first) 3. **Changing `max_length`** (data truncation risk) ### 🟢 LOW RISK - Generally Safe 1. **Adding nullable fields** 2. **Adding fields with defaults** 3. **Creating new tables** 4. **Adding non-unique indexes** ## Validation Process ### Step 1: Analyze Migration File When migration is created: ```python # Generated migration class Migration(migra