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withPgClient and withPgClientTransaction

Sometimes you want to use your PostgreSQL client directly, e.g. to run arbitrary SQL, or use your specific database client's helper methods; that's what withPgClient is there to help you with.

danger

Like lambda, withPgClient is an escape hatch and does not use batching.

withPgClient(executor, $data, callback)​

You need to pass three arguments to withPgClient:

  • executor - this is needed to connect to the database; you can grab the executor from the registry directly or any of the resources that you have in the same database
  • $data - an arbitrary step representing the data that your callback needs; set this to constant(null) if you don't need anything
  • callback(client, data) - the (async) function to be called with the database client and the data from your $data step

withPgClient will grab a client from the context, call your callback and wait for it to return, and then release the client again, ultimately resolving to the return result of your callback.

import { withPgClient } from "@dataplan/pg";
import { constant } from "grafast";
import { registry } from "./myRegistry";

// Grab executor from the registry
const executor = pgRegistry.pgExecutors.main;

function meaningOfLifePlan() {
  // Arbitrary data for our callback to use
  const $twenty = constant(20);

  // 20 + 22 = 42
  const $meaningOfLife = withPgClient(
    executor,
    $twenty,
    async (client, twenty) => {
      // The client that you receive will be dependent on the adaptor you're
      // using, but must have a `query` method:
      const {
        rows: [{ num }],
      } = await client.query({ text: `select 22 as num` });

      return twenty + parseInt(num, 10);
    },
  );

  return $meaningOfLife;
}

withPgClientTransaction(executor, $data, callback)​

Exactly the same as withPgClient except it starts a transaction before calling callback and commits it when callback completes successfully or rolls it back if an error is raised.