managarten/.claude/guidelines/database.md

Database Guidelines

Overview

All projects use Drizzle ORM with PostgreSQL. This document covers schema design patterns, naming conventions, and migration strategies.

ORM: Drizzle

Why Drizzle?

• Full TypeScript type inference
• SQL-like syntax (no magic)
• Lightweight and fast
• Excellent PostgreSQL support

Connection Pattern

// src/db/connection.ts
import { drizzle } from 'drizzle-orm/postgres-js';
import postgres from 'postgres';
import * as schema from './schema';

let connection: ReturnType<typeof postgres> | null = null;
let db: ReturnType<typeof drizzle> | null = null;

export function getConnection(databaseUrl: string) {
	if (!connection) {
		connection = postgres(databaseUrl, {
			max: 10, // Max connections
			idle_timeout: 20, // Seconds before closing idle
			connect_timeout: 10, // Connection timeout
		});
	}
	return connection;
}

export function getDb(databaseUrl: string) {
	if (!db) {
		const conn = getConnection(databaseUrl);
		db = drizzle(conn, { schema });
	}
	return db;
}

export async function closeConnection() {
	if (connection) {
		await connection.end();
		connection = null;
		db = null;
	}
}

export type Database = ReturnType<typeof getDb>;

NestJS Integration

// src/db/database.module.ts
import { Global, Module, OnModuleDestroy } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { getDb, closeConnection, Database } from './connection';

export const DATABASE_CONNECTION = 'DATABASE_CONNECTION';

@Global()
@Module({
	providers: [
		{
			provide: DATABASE_CONNECTION,
			useFactory: (configService: ConfigService): Database => {
				const databaseUrl = configService.get<string>('DATABASE_URL');
				return getDb(databaseUrl);
			},
			inject: [ConfigService],
		},
	],
	exports: [DATABASE_CONNECTION],
})
export class DatabaseModule implements OnModuleDestroy {
	async onModuleDestroy() {
		await closeConnection();
	}
}

Schema Design

File Organization

src/db/
├── schema/
│   ├── index.ts           # Exports all schemas
│   ├── users.schema.ts    # User-related tables
│   ├── files.schema.ts    # File-related tables
│   └── ...
├── connection.ts          # DB connection singleton
├── database.module.ts     # NestJS module
└── migrations/            # Generated migrations

Table Definition Pattern

// src/db/schema/files.schema.ts
import {
	pgTable,
	uuid,
	varchar,
	text,
	boolean,
	timestamp,
	bigint,
	integer,
} from 'drizzle-orm/pg-core';
import { relations } from 'drizzle-orm';

export const files = pgTable(
	'files',
	{
		// Primary key - always UUID with auto-generation
		id: uuid('id').primaryKey().defaultRandom(),

		// Foreign keys
		userId: varchar('user_id', { length: 255 }).notNull(),
		parentFolderId: uuid('parent_folder_id').references(() => folders.id, { onDelete: 'set null' }),

		// Required fields
		name: varchar('name', { length: 500 }).notNull(),
		mimeType: varchar('mime_type', { length: 255 }).notNull(),
		size: bigint('size', { mode: 'number' }).notNull(),
		storagePath: varchar('storage_path', { length: 1000 }).notNull(),
		storageKey: varchar('storage_key', { length: 500 }).notNull().unique(),

		// Optional fields
		description: text('description'),

		// Boolean flags with defaults
		isFavorite: boolean('is_favorite').default(false).notNull(),
		isPublic: boolean('is_public').default(false).notNull(),

		// Soft delete
		isDeleted: boolean('is_deleted').default(false).notNull(),
		deletedAt: timestamp('deleted_at', { withTimezone: true }),

		// Timestamps - ALWAYS include these
		createdAt: timestamp('created_at', { withTimezone: true }).defaultNow().notNull(),
		updatedAt: timestamp('updated_at', { withTimezone: true }).defaultNow().notNull(),
	},
	(table) => ({
		// Indexes for common queries
		userIdIdx: index('idx_files_user_id').on(table.userId),
		parentFolderIdx: index('idx_files_parent_folder').on(table.parentFolderId),
		createdAtIdx: index('idx_files_created_at').on(table.createdAt),
	})
);

// Type exports - ALWAYS include these
export type File = typeof files.$inferSelect;
export type NewFile = typeof files.$inferInsert;

Relations

// Define relations separately for clarity
export const filesRelations = relations(files, ({ one, many }) => ({
	folder: one(folders, {
		fields: [files.parentFolderId],
		references: [folders.id],
	}),
	versions: many(fileVersions),
	tags: many(fileTags),
}));

export const foldersRelations = relations(folders, ({ one, many }) => ({
	parent: one(folders, {
		fields: [folders.parentFolderId],
		references: [folders.id],
		relationName: 'parentChild',
	}),
	children: many(folders, { relationName: 'parentChild' }),
	files: many(files),
}));

Naming Conventions

Tables

Rule	Example
Use snake_case	user_sessions, file_versions
Use plural nouns	users, files, tags
Junction tables: {entity1}_{entity2}	file_tags, user_roles

Columns

Type	Convention	Example
Primary key	id	id
Foreign key	{entity}_id	user_id, folder_id
Boolean	is_ or has_ prefix	is_deleted, has_password
Timestamp	_at suffix	created_at, deleted_at
Count	_count suffix	download_count
Version	version or current_version	version

Indexes

// Pattern: idx_{table}_{column(s)}
index('idx_files_user_id').on(table.userId);
index('idx_files_created_at').on(table.createdAt);
index('idx_messages_conversation_created').on(table.conversationId, table.createdAt);

Common Patterns

1. Soft Deletes

// Schema
isDeleted: boolean('is_deleted').default(false).notNull(),
deletedAt: timestamp('deleted_at', { withTimezone: true }),

// Query - always filter out deleted
const activeFiles = await db
  .select()
  .from(files)
  .where(and(
    eq(files.userId, userId),
    eq(files.isDeleted, false)  // Always include this
  ));

// Soft delete
await db
  .update(files)
  .set({ isDeleted: true, deletedAt: new Date() })
  .where(eq(files.id, fileId));

// Hard delete (permanent)
await db
  .delete(files)
  .where(eq(files.id, fileId));

2. Timestamps

// Schema - always include both
createdAt: timestamp('created_at', { withTimezone: true }).defaultNow().notNull(),
updatedAt: timestamp('updated_at', { withTimezone: true }).defaultNow().notNull(),

// Update - always set updatedAt
await db
  .update(files)
  .set({ name: newName, updatedAt: new Date() })
  .where(eq(files.id, fileId));

3. Optimistic Locking (for concurrent updates)

// Schema
version: integer('version').default(1).notNull(),

// Update with version check
const [updated] = await db
  .update(balances)
  .set({
    amount: newAmount,
    version: sql`version + 1`,
    updatedAt: new Date(),
  })
  .where(and(
    eq(balances.userId, userId),
    eq(balances.version, currentVersion)  // Only update if version matches
  ))
  .returning();

if (!updated) {
  return err(ErrorCode.CONFLICT, 'Balance was modified by another operation');
}

4. JSONB for Flexible Data

// Schema
metadata: jsonb('metadata').$type<Record<string, unknown>>(),
settings: jsonb('settings').default({}).$type<UserSettings>(),
tags: jsonb('tags').$type<string[]>().default([]),

// Query JSONB
const usersWithTag = await db
  .select()
  .from(users)
  .where(sql`${users.tags} @> '["premium"]'::jsonb`);

5. Enums

// Define enum
export const transactionTypeEnum = pgEnum('transaction_type', [
  'purchase',
  'usage',
  'refund',
  'bonus',
  'adjustment',
]);

// Use in table
type: transactionTypeEnum('type').notNull(),

// TypeScript type
type TransactionType = typeof transactionTypeEnum.enumValues[number];

6. Pagination

async function getPaginated(
	userId: string,
	page: number = 1,
	limit: number = 20
): Promise<Result<{ items: File[]; total: number }>> {
	const offset = (page - 1) * limit;

	const [items, countResult] = await Promise.all([
		db
			.select()
			.from(files)
			.where(and(eq(files.userId, userId), eq(files.isDeleted, false)))
			.orderBy(desc(files.createdAt))
			.limit(limit)
			.offset(offset),
		db
			.select({ count: sql<number>`count(*)` })
			.from(files)
			.where(and(eq(files.userId, userId), eq(files.isDeleted, false))),
	]);

	return ok({ items, total: countResult[0].count });
}

Migrations

Configuration

// drizzle.config.ts
import { defineConfig } from 'drizzle-kit';

export default defineConfig({
	schema: './src/db/schema/index.ts',
	out: './src/db/migrations',
	driver: 'pg',
	dbCredentials: {
		connectionString: process.env.DATABASE_URL!,
	},
	verbose: true,
	strict: true,
});

Commands

# Generate migration from schema changes
pnpm drizzle-kit generate

# Push schema directly (development only)
pnpm drizzle-kit push

# Open Drizzle Studio
pnpm drizzle-kit studio

# Run migrations (production)
pnpm db:migrate

Migration Runner

// src/db/migrate.ts
import { drizzle } from 'drizzle-orm/postgres-js';
import { migrate } from 'drizzle-orm/postgres-js/migrator';
import postgres from 'postgres';

async function runMigrations() {
	const connection = postgres(process.env.DATABASE_URL!, { max: 1 });
	const db = drizzle(connection);

	console.log('Running migrations...');
	await migrate(db, { migrationsFolder: './src/db/migrations' });
	console.log('Migrations complete');

	await connection.end();
}

runMigrations().catch(console.error);

Query Patterns

Select with Joins

const filesWithTags = await db
	.select({
		file: files,
		tags: sql<string[]>`array_agg(${tags.name})`,
	})
	.from(files)
	.leftJoin(fileTags, eq(files.id, fileTags.fileId))
	.leftJoin(tags, eq(fileTags.tagId, tags.id))
	.where(eq(files.userId, userId))
	.groupBy(files.id);

Transactions

const result = await db.transaction(async (tx) => {
	// All operations in same transaction
	const [file] = await tx.insert(files).values(newFile).returning();

	await tx.insert(fileVersions).values({ fileId: file.id, versionNumber: 1 });

	return file;
});

Upsert

await db
	.insert(userSettings)
	.values({ userId, theme: 'dark' })
	.onConflictDoUpdate({
		target: userSettings.userId,
		set: { theme: 'dark', updatedAt: new Date() },
	});

Anti-Patterns

1. N+1 Queries

// BAD - N+1 queries
const files = await db.select().from(files);
for (const file of files) {
	const tags = await db.select().from(tags).where(eq(tags.fileId, file.id)); // N queries!
}

// GOOD - Single query with join
const filesWithTags = await db
	.select()
	.from(files)
	.leftJoin(fileTags, eq(files.id, fileTags.fileId))
	.leftJoin(tags, eq(fileTags.tagId, tags.id));

2. Missing Indexes

// If you frequently query by a column, add an index
// BAD - No index on frequently queried column
const userFiles = await db.select().from(files).where(eq(files.userId, userId));

// GOOD - Index defined in schema
}, (table) => ({
  userIdIdx: index('idx_files_user_id').on(table.userId),
}));

3. Storing Derived Data

// BAD - Storing calculated totals that can become stale
totalFiles: integer('total_files'),

// GOOD - Calculate when needed
const { count } = await db
  .select({ count: sql<number>`count(*)` })
  .from(files)
  .where(eq(files.folderId, folderId));