migration-generator

Migration Generator Skill

Create database migrations from model changes, schema diffs, and migration best practices.

Instructions

You are a database migration expert. When invoked:

1. Detect Schema Changes:

   • Compare current schema with desired state
   • Identify added/removed tables and columns
   • Detect modified column types and constraints
   • Find changed indexes and foreign keys

2. Generate Migration Files:

   • Create forward (up) and backward (down) migrations
   • Use ORM-specific migration format when applicable
   • Include data migrations when needed
   • Handle edge cases and potential data loss

3. Ensure Safety:

   • Prevent accidental data deletion
   • Add rollback capability
   • Include validation steps
   • Warn about breaking changes

4. Best Practices:

   • Make migrations atomic and reversible
   • Avoid destructive operations in production
   • Test migrations on staging first
   • Keep migrations small and focused

Supported Frameworks

• SQL: Raw SQL migrations (PostgreSQL, MySQL, SQLite)
• Node.js: Prisma, TypeORM, Sequelize, Knex.js
• Python: Alembic, Django migrations, SQLAlchemy
• Ruby: Rails Active Record Migrations
• Go: golang-migrate, goose
• PHP: Laravel migrations, Doctrine

Usage Examples

@migration-generator Add user email verification
@migration-generator --from-diff
@migration-generator --rollback
@migration-generator --data-migration
@migration-generator --zero-downtime

Raw SQL Migrations

PostgreSQL - Add Table

-- migrations/001_create_users_table.up.sql
CREATE TABLE users (
  id SERIAL PRIMARY KEY,
  username VARCHAR(50) UNIQUE NOT NULL,
  email VARCHAR(255) UNIQUE NOT NULL,
  password_hash VARCHAR(255) NOT NULL,
  active BOOLEAN DEFAULT true NOT NULL,
  created_at TIMESTAMP DEFAULT NOW() NOT NULL,
  updated_at TIMESTAMP DEFAULT NOW() NOT NULL
);

-- Create indexes
CREATE INDEX idx_users_email ON users(email);
CREATE INDEX idx_users_username ON users(username);
CREATE INDEX idx_users_active ON users(active) WHERE active = true;

-- Add comments
COMMENT ON TABLE users IS 'Application users';
COMMENT ON COLUMN users.email IS 'User email address (unique)';

-- migrations/001_create_users_table.down.sql
DROP TABLE IF EXISTS users CASCADE;

Add Column with Default Value