# DB Schema Change

> Handle Drizzle database schema changes safely. Generate and apply migrations, add tables and columns. Use when modifying database schema, adding tables, creating migrations, or making database changes. Use when this capability is needed.

- Skill: `tomevault-io/db-schema-change-2` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/db-schema-change-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/db-schema-change-2/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/db-schema-change-2

---


# 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

| File                             | Purpose               |
| -------------------------------- | --------------------- |
| `packages/db/src/schema.ts`      | Main schema exports   |
| `packages/db/src/auth-schema.ts` | Better Auth tables    |
| `packages/db/src/rag-schema.ts`  | RAG embeddings tables |
| `packages/db/drizzle/`           | Generated migrations  |

## 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:

```typescript
// 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:

```bash
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)

```bash
pnpm -C packages/db migrate:apply
```

### Step 7: Verify

```bash
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)

---
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<!-- tomevault:4.0:skill_md:2026-04-11 -->