Scrum4Me/docs/patterns/prisma-client.md

title	status	audience	language	last_updated	when_to_read
Prisma Client singleton	active	ai-agent contributor	nl	2026-05-03	When importing or initialising the Prisma client in server code.

Patroon: Prisma Client singleton

lib/prisma.ts

PostgreSQL via pg + @prisma/adapter-pg (Neon/Vercel).

import { PrismaClient } from '@prisma/client'
import { Pool } from 'pg'
import { PrismaPg } from '@prisma/adapter-pg'

function createPrismaClient() {
  const url = process.env.DATABASE_URL
  if (!url) throw new Error('DATABASE_URL is not set')

  const pool = new Pool({ connectionString: url })
  const adapter = new PrismaPg(pool)
  return new PrismaClient({
    adapter,
    log: process.env.NODE_ENV === 'development' ? ['error', 'warn'] : ['error'],
  })
}

const globalForPrisma = globalThis as unknown as { prisma: PrismaClient | undefined }

export const prisma = globalForPrisma.prisma ?? createPrismaClient()

if (process.env.NODE_ENV !== 'production') globalForPrisma.prisma = prisma

prisma.config.ts (Prisma v7 vereiste)

import 'dotenv/config'
import { defineConfig } from 'prisma/config'

export default defineConfig({
  schema: 'prisma/schema.prisma',
  migrations: { path: 'prisma/migrations' },
})

Prisma generators

prisma/schema.prisma bevat twee generators:

generator client {
  provider = "prisma-client-js"
}

generator erd {
  provider = "prisma-erd-generator"
  output   = "../docs/assets/erd.svg"
}

prisma generate bouwt dus twee artifacts:

• Prisma Client in node_modules/@prisma/client
• het ERD-diagram in docs/assets/erd.svg

Gebruik volledige prisma generate alleen lokaal. De ERD-generator gebruikt Mermaid/Puppeteer en mag niet in CI of Vercel draaien.

Commands

Command	Gebruik
npx prisma db push	Schema synchroniseren naar de database
npx prisma db seed	Seeddata laden
npx prisma generate --generator client	Alleen Prisma Client genereren; gebruiken in CI/deployment
npm run db:erd	prisma generate: Prisma Client en docs/assets/erd.svg genereren
npm run db:erd:watch	prisma/schema.prisma watchen en ERD opnieuw genereren
npm run dev	Next.js dev server plus ERD watcher starten

Belangrijk: db push schrijft naar de database, maar genereert geen ERD. Gebruik na schemawijzigingen lokaal npm run db:erd of laat npm run dev de watcher draaien. Gebruik in CI en deployment alleen npx prisma generate --generator client.