dataloader VS ava

When I began working with GraphQL, I had concerns about the N+1 query problem. In my research, I came across the DataLoader pattern and its implementation on GitHub. While I explored various examples of its usage, I still struggled to grasp how it operates internally. Join me in delving a bit deeper into GraphQL DataLoader! :)

DataLoader: it is the standard solution to N+1 problem.

Additionally, you can use DataLoader or similar tools to optimize data fetching and avoid over-fetching or under-fetching data. Ultimately, performance and load tests ensure that your GraphQL API delivers optimal performance, meets response time expectations, and provides a smooth experience for users, even under heavy loads.

The most common practice is to turn N+1 into 1+1 using dataloaders (https://github.com/graphql/dataloader for JS, there are equivalents for most implementations). The N resolvers invoke a single batched loader which receives a list of keys and returns a list of values.

Let's take Payload, for example. Surprise, surprise. We have a relationship field, and it can store IDs to other related documents which are seamlessly merged in when you retrieve documents from the DB. We leverage the dataloader pattern to batch together all "populations" required for a given query, returning them all super fast and with as few separate queries to the DB as possible. We actually even outperform SQL-based frameworks quite a bit. In a purely relational test, we were 3x faster than Directus and 7x faster than Strapi while both were running Postgres, and we were on MongoDB.

Also, have a look at Facebook's Dataloader[0].

[0] https://github.com/graphql/dataloader

In the next article, I'm going to implement a GraphQL server with dataloader using the tools we introduced.

The one example of using Scoped dependency that comes to my mind, it's HTTP request level caching for libs like dataloader.

you would fetch these 1000 rows via dataloader that batches all requests for this relation to a single query... solving the n+1 issue

We use Jest Framework for testing. Jest is not a dogma, and, of course, in its place can be any other test runner, such as Mocha or Ava. Let's focus on tests. I'll provide a short example because I don’t want to waste your time. You can find the full version here. It's crucial to read the comments in the code below. Let's go!

> In the popular jest test runner, each test file is executed in its own child process.

Is that confirmed?

I've been following this issue:

https://github.com/jestjs/jest/issues/6957

And what Jest actually does is still kind of muddy.

In contrast to that, other test runners like AVA have a clear description what happens when:

https://github.com/avajs/ava/blob/main/docs/01-writing-tests...

I've been looking at using japa or ava for web server testing but was curious what others were using and why.

Continued work on the test suite. Implementing AVA, with snapshotting. Making a lot of effort to have the snapshot directory structure match the test262 test directory structure by generating AVA test files.

You might want to give ava a spin:

https://github.com/avajs/ava/

It has a TAP reporter, but more importantly, as opposed to the more popular solutions, like Jest, the way it achieves parallelism is explained in the docs and won't change anytime soon, thus preventing wonky, hard to debug errors which occur when this part is abstracted away.

I switched to ava for that reason and have been very happy with it. But vitest looks nice, too. Thanks for the pointer.

Runs unit tests using AVA.

Last but not least important are ava, uvu and tape; they are a really light and fast test runners.

I've had some good experiences with Ava + Sinon. I've personally disliked Jest because it seemed to do some weird trickery in the background that prevented me from using ES modules.

Ava for a simpler environment than Jest, which I usually use. I need to check how to mock ESM with it, though.