How can I use slonik with an existing pg.Client?

[innermatrix]

I am working with a 3rd party package that sets up a pg.Client for me and passes it into my code. I want to use slonik utilities with this pg.Client rather than creating a separate db connection. How can I accomplish this? Thanks!

[AndrewJo]

Slonik doesn't let you point to your own instance of pg.Client directly (for good reason), it uses pg.Pool to checkout a client when a connection needs to be made.

However, you can specify a constructor to the pg.Pool in the createPool options which means you can extend pg.Pool and return your custom client.

import { Pool } from "pg";
import { createPool } from "slonik";

const client = pgClientFromSomeLibrary();

// Do whatever you want here to extend the pool behavior including re-using existing pg.Client instance here.
class CustomPool extends Pool {
  constructor(config) {
    super(config);
  }

  async connect() {
    // Override the connect method to return the existing pg.Client instance; 
    // UNDERSTAND THE CAVEATS AND IMPLICATIONS FOR DOING THIS SINCE YOU'RE ALWAYS CHECKING OUT
    // THE SAME CLIENT INSTANCE. YOU MAY NEED TO CLONE INSTANCES AND RETURN THOSE INSTEAD.
    return client;
  }
}

const customPool = await createPool("postgres://", {
  // Specify the custom pool class here for Slonik to use under the hood
  PgPool: CustomPool
});

However, just because you can doesn't mean you should! Doing this will most likely break pool management behavior of Slonik so you should be really REALLY sure you need to override PgPool!

[innermatrix]

Thanks. As I mentioned in my question, the goal is to use slonik utils with a pg.Client obtained from another library, not to take advantage of pool management, so that's exactly what I need.