PostgreSQL + Drizzle ORM Skill

PostgreSQL + Drizzle ORM

Type-safe database applications with PostgreSQL 18 and Drizzle ORM.

Essential Commands

npx drizzle-kit generate   # Generate migration from schema changes
npx drizzle-kit migrate    # Apply pending migrations
npx drizzle-kit push       # Push schema directly (dev only!)
npx drizzle-kit studio     # Open database browser

Quick Decision Trees

"How do I model this relationship?"

Relationship type?
├─ One-to-many (user has posts)     → FK on "many" side + relations()
├─ Many-to-many (posts have tags)   → Junction table + relations()
├─ One-to-one (user has profile)    → FK with unique constraint
└─ Self-referential (comments)      → FK to same table

"Why is my query slow?"

Slow query?
├─ Missing index on WHERE/JOIN columns  → Add index
├─ N+1 queries in loop                  → Use relational queries API
├─ Full table scan                      → EXPLAIN ANALYZE, add index
├─ Large result set                     → Add pagination (limit/offset)
└─ Connection overhead                  → Enable connection pooling

"Which drizzle-kit command?"

What do I need?
├─ Schema changed, need SQL migration   → drizzle-kit generate
├─ Apply migrations to database         → drizzle-kit migrate
├─ Quick dev iteration (no migration)   → drizzle-kit push
└─ Browse/edit data visually            → drizzle-kit studio

Directory Structure

src/db/
├── schema/
│   ├── index.ts          # Re-export all tables
│   ├── users.ts          # Table + relations
│   └── posts.ts          # Table + relations
├── db.ts                 # Connection with pooling
└── migrate.ts            # Migration runner
drizzle/
└── migrations/           # Generated SQL files
drizzle.config.ts         # drizzle-kit config

Schema Patterns

Basic Table with Timestamps

export const users = pgTable('users', {
  id: uuid('id').primaryKey().defaultRandom(),
  email: varchar('email', { length: 255 }).notNull().unique(),
  createdAt: timestamp('created_at').defaultNow().notNull(),
  updatedAt: timestamp('updated_at').defaultNow().notNull(),
});

Foreign Key with Index

export const posts = pgTable('posts', {
  id: uuid('id').primaryKey().defaultRandom(),
  userId: uuid('user_id').notNull().references(() => users.id),
  title: varchar('title', { length: 255 }).notNull(),
}, (table) => [
  index('posts_user_id_idx').on(table.userId), // ALWAYS index FKs
]);

Relations

export const usersRelations = relations(users, ({ many }) => ({
  posts: many(posts),
}));

export const postsRelations = relations(posts, ({ one }) => ({
  author: one(users, { fields: [posts.userId], references: [users.id] }),
}));

Query Patterns

Relational Query (Avoid N+1)

// ✓ Single query with nested data
const usersWithPosts = await db.query.users.findMany({
  with: { posts: true },
});

Filtered Query

const activeUsers = await db
  .select()
  .from(users)
  .where(eq(users.status, 'active'));

Transaction

await db.transaction(async (tx) => {
  const [user] = await tx.insert(users).values({ email }).returning();
  await tx.insert(profiles).values({ userId: user.id });
});

Performance Checklist

| Priority | Check | Impact | |----------|-------|--------| | CRITICAL | Index all foreign keys | Prevents full table scans on JOINs | | CRITICAL | Use relational queries for nested data | Avoids N+1 | | HIGH | Connection pooling in production | Reduces connection overhead | | HIGH | EXPLAIN ANALYZE slow queries | Identifies missing indexes | | MEDIUM | Partial indexes for filtered subsets | Smaller, faster indexes | | MEDIUM | UUIDv7 for PKs (PG18+) | Better index locality |

Anti-Patterns (CRITICAL)

| Anti-Pattern | Problem | Fix | |--------------|---------|-----| | No FK index | Slow JOINs, full scans | Add index on every FK column | | N+1 in loops | Query per row | Use with: relational queries | | No pooling | Connection per request | Use @neondatabase/serverless or similar | | push in prod | Data loss risk | Always use generate + migrate | | Storing JSON as text | No validation, bad queries | Use jsonb() column type |

Reference Documentation

| File | Purpose | |------|---------| | references/SCHEMA.md | Column types, constraints | | references/QUERIES.md | Operators, joins, aggregations | | references/RELATIONS.md | One-to-many, many-to-many | | references/MIGRATIONS.md | drizzle-kit workflows | | references/POSTGRES.md | PG18 features, RLS, partitioning | | references/PERFORMANCE.md | Indexing, optimization | | references/CHEATSHEET.md | Quick reference |

Resources

Drizzle ORM

Official Documentation: https://orm.drizzle.team
GitHub Repository: https://github.com/drizzle-team/drizzle-orm
Drizzle Kit (Migrations): https://orm.drizzle.team/kit-docs/overview

PostgreSQL

Official Documentation: https://www.postgresql.org/docs/
SQL Commands Reference: https://www.postgresql.org/docs/current/sql-commands.html
Performance Tips: https://www.postgresql.org/docs/current/performance-tips.html
Index Types: https://www.postgresql.org/docs/current/indexes-types.html
JSON Functions: https://www.postgresql.org/docs/current/functions-json.html
Row Level Security: https://www.postgresql.org/docs/current/ddl-rowsecurity.html

Agent Skills: PostgreSQL + Drizzle ORM

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