Database Schema Change

Safely modify PostgreSQL schema using Drizzle ORM.

When to Use

• "Add a new table for..."
• "Add column to..."
• "Create migration for..."
• "Modify database schema"
• "Add foreign key to..."

Important Files

Procedure

Step 1: Understand Current Schema

Read the schema file to understand existing tables:

Read: packages/db/src/schema.ts

Step 2: Plan the Change

Before making changes, confirm with user:

• Table name and column definitions
• Data types (see [types.md](./types.md))
• Relationships (foreign keys)
• Indexes needed
• Whether data migration is required

Step 3: Modify Schema

Edit the appropriate schema file:

// packages/db/src/schema.ts
import { pgTable, text, timestamp, uuid } from 'drizzle-orm/pg-core';

export const newTable = pgTable('new_table', {
  id: uuid('id').primaryKey().defaultRandom(),
  name: text('name').notNull(),
  createdAt: timestamp('created_at').defaultNow().notNull(),
  updatedAt: timestamp('updated_at').defaultNow().notNull(),
});

Step 4: Generate Migration

Run migration generator:

pnpm -C packages/db migrate:generate

Step 5: Review Migration

Read the generated migration in packages/db/drizzle/ and verify:

• Correct SQL statements
• No data loss for existing tables
• Proper indexes created

Step 6: Apply Migration (Local)

pnpm -C packages/db migrate:apply

Step 7: Verify

pnpm typecheck
pnpm lint

Checklist

• Schema change planned with user
• Schema file updated
• Migration generated
• Migration reviewed (no data loss)
• Migration applied locally
• TypeScript compiles
• Existing tests still pass

Guardrails

• NEVER drop columns without explicit user confirmation
• NEVER run migrations on production directly (CI handles this)
• ALWAYS generate migration before applying
• ALWAYS review generated SQL before applying
• If migration involves data transformation, create separate script
• Ask user before destructive changes (DROP, TRUNCATE)