Add drizzle singleton snippet code to docs

[lucaspiresfernandes]

In order to use drizzle with Next.js for example, you have to create a singleton connection so that it persists between reloads. It's not clear as how to do it and if you don't, you'll have to restart you development environment every other minute because of the database server complaints. Most people don't know how to set it up and even I struggled to find a solution. Well, now that I have, I would like to share it and I think it would be a good idea to add it to the docs. Here's the code:

// lib/db.ts

import { drizzle } from 'drizzle-orm/postgres-js';
import postgres, { Sql } from 'postgres';
import * as schema from 'schema';

let connection: Sql<{}>;

if (process.env.NODE_ENV === 'production') {
  connection = postgres(process.env.DATABASE_URL);
} else {
  let globalConnection = global as typeof globalThis & {
    connection: Sql<{}>;
  };

  if (!globalConnection.connection) globalConnection.connection = postgres(process.env.DATABASE_URL);

  connection = globalConnection.connection;
}

const db = drizzle(connection, { schema, logger: process.env.NODE_ENV !== 'production' });

export default db;

[Sparticuz]

I have issues with this. My page will work fine the first time, but then I'll randomly start getting this error:

 ⨯ Error: Your "contractAmount" field references a column "view_customers"."contract_amount", but the table "view_customers" is not part of the query! Did you forget to join it?
    at MySqlDialect.buildSelectQuery (webpack-internal:///(rsc)/./node_modules/drizzle-orm/mysql-core/dialect.js:185:15)
    at MySqlSelectBase.getSQL (webpack-internal:///(rsc)/./node_modules/drizzle-orm/mysql-core/query-builders/select.js:658:25)
    at MySqlSelectBase.prepare (webpack-internal:///(rsc)/./node_modules/drizzle-orm/mysql-core/query-builders/select.js:688:74)
    at MySqlSelectBase.execute (webpack-internal:///(rsc)/./node_modules/drizzle-orm/mysql-core/query-builders/select.js:693:17)
    at MySqlSelectBase.then (webpack-internal:///(rsc)/./node_modules/drizzle-orm/query-promise.js:26:17)

I've tried the above singleton, as well as something similar from Prisma's docs. Production seems to work fine though. 🤷‍♂️

Hmm, I wonder if it has something to do with schema table factories

const customersView = getCustomersView(region);
const customers = await database
  .select({
    contractAmount: customersView.contractAmount,
    custName: customersView.custName,
    endDate: customersView.endDate,
    fullFranName: customersView.fullFranName,
    id: customersView.id,
    opsTeamName: customersView.opsTeamName,
    salesRep: customersView.salesRep,
    serviceAddress: customersView.serviceAddress,
    startDate: customersView.startDate,
    statusName: customersView.statusName,
  })
  .from(customersView);