node.jsprisma

How to create a single Prisma instance in Next.js development env?

I am using Prisma and Next.js in development env, and I found multiple 'database connection initialized' printed when page hot-reloaded

import { PrismaClient } from "@prisma/client";

declare global {
  var db: PrismaClient | undefined;
}

const create = () => {
  console.log('database connection initialized');
  return new PrismaClient()
}

const db = global.db || create();

if (process.env.NODE_ENV !== "production") global.db = db;

export {db}

This can lead to multiple instances of Prisma client being created, which consumes resources and might cause unexpected behavior.

How could I do this correctly?

Solution

  • Try to do something like this :

    import { PrismaClient } from "@prisma/client";

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

export const db =
  globalForPrisma.prisma ??
  new PrismaClient({
    // log: ['query'], // optionally log SQL queries in dev
  });

if (process.env.NODE_ENV !== "production") globalForPrisma.prisma = db;

    And I will try to explain as well as I can