DB Migration Skill

Goal

Implement database schema changes safely using migration-first development. All migrations must be reversible and tested before applying to production.

Steps

1. Inspect current schema

   • Read current migration files to understand existing schema
   • Check: any foreign key constraints that would be affected?
   • Check: any indexes on columns being modified?
   • Check: any application code relying on the current schema shape?

2. Design the schema change

   • Minimal change to achieve the goal
   • Consider backward compatibility:
     • Adding nullable column: backward compatible ✓
     • Adding NOT NULL column without default: breaking ✗
     • Renaming column: breaking ✗ (use add → populate → rename → drop strategy)
     • Changing column type: potentially breaking — check data conversion