Cloudflare で Prisma + PostgreSQL を使う場合、リクエストを超えてインスタンスを使いまわしてはいけない

1export * from "@prisma/adapter-pg";
2import { Pool } from "pg";
3import { PrismaPg } from "@prisma/adapter-pg";
4import { PrismaClient } from "@prisma/client";
5
6export interface Env {
7  DATABASE_URL: string;
8  prisma: Fetcher;
9}
10
11// Errors occur when Prisma instances are used around.
12let prisma: PrismaClient;
13
14export default {
15  async fetch(
16    request: Request,
17    env: Env,
18    _ctx: ExecutionContext
19  ): Promise<Response> {
20    const url = new URL(request.url);
21    if (url.pathname !== "/") return new Response("Not Found", { status: 404 });
22    if (!prisma) {
23      const databaseUrl = new URL(env.DATABASE_URL);
24      const schema = databaseUrl.searchParams.get("schema") ?? undefined;
25      const pool = new Pool({
26        connectionString: env.DATABASE_URL,
27      });
28      const adapter = new PrismaPg(pool, { schema });
29      prisma = new PrismaClient({ adapter });
30    }
31    await prisma.test.create({ data: {} });
32    const result = await prisma.test
33      .findMany()
34      .then((r) => r.map(({ id }) => id));
35    return new Response(JSON.stringify(result, undefined, "  "), {
36      headers: { "content-type": "application/json" },
37    });
38  },
39};