Helper functions

Hey, I use these two helper functions in pretty much every project I use node-postgres in. I was just wondering if you’d be open to a PR to add these to the project proper?

export async function withClient(pool: Pool, fn: (client: PoolClient) => Promise<void>) {
    const client = await pool.connect();
    try {
        await fn(client);
    } finally {
        client.release();
    }
}

export async function withTransaction(pool: Pool, fn: (client: PoolClient) => Promise<void>) {
    await withClient(async client => {
        try {
            await client.query('BEGIN');
            await fn(client);
            await client.query('COMMIT');
        } catch (e) {
            await client.query('ROLLBACK');
            throw e;
        }
    });
}

The basic idea here is I can do:

await withTransaction(pool, async client => {
    client.query(...);
});

and then there’s no chance of me messing up and forgetting the ROLLBACK or forgetting to release the client from the pool; it all gets handled for me. If you’re interested, I’ll do up a PR and write some docs.

[brianc]

I also think that pg could be offering slightly nicer helpers for these things by default, to avoid people running into common traps of forgetting to release clients, rollback transactions, etc.

I agree with you - most of those traps are due to me designing a…maybe not the best…api a long time ago and trying hard to limit backwards incompatible breaks. query queuing, emitting row events, manually releasing clients, being really opinionated with timezones and type coercion, etc…are all things I could have done a better job of a long time ago. Now it’s a careful dance of weighing the cost of forcing thousands of folks to change their apps versus maintaining things which aren’t very nice or intuitive. I’ve focused this year on improving performance (we’re up something like 30-40% from 7.x branch) and will likely start the work of deprecating and slowly sweeping away some of those bad decisions in 2021. I planned on more of that in 2020 but you know 2020 wasn’t the very best year for focus/productivity while the world has been on fire. ❤️ 😬

I will say if you feel the pain I feel it 10x.

[brianc]

I’m down to merge something like this if it’s sufficiently tested! I think ideally you could create another project in the monorepo like pg-fns or something & add it there. Then you could write it with sweet, sweet typescript. Currently converting the core pg module to typescript is something I’ve fiddled with locally a few times but isn’t quite in scope yet, and would 100% be a semver major just because typescript is gonna fiddle w/ the internals of things enough to likely break a bunch of integrations and stuff (things like datadog and sentry sometimes poke deeply into the module’s code). That would also keep anyone who wants the main package “clean” to have it their way, and I could long term own the maintenance and documentation of pg-fns (with help from the community of course!) This would hopefully allow on-boarding into the ecosystem to be easier, reduce having to write the slightly finicky withTransaction function yourself in every project, might be a cool place for new contributors to contribute to, etc.

The name of the module can be whatever you want - I just picked pg-fns because it’s available on npm. Apparently a lot of pg-* modules are taken already 🙃