Loader

Loader is the core primitive of data fetching used by the framework. It's used by the generated code to fetch data and retrieve from the context cache as needed.

This section is only relevant when writing custom queries or to peek under the hood to figure out how things work.

The Loader API looks like this:

export interface Loader<T, V> {
  context?: Context;
  load(key: T): Promise<V>;
  loadMany?(keys: T[]): Promise<(V | null)[]>;
  clearAll(): any;
}

Most Loaders use DataLoader to fetch data but that's an implementation detail. The Loader API is agnostic to how data is fetched and if it's cached.

LoaderFactory

As the name suggests, LoaderFactory is a factory instance used to create Loaders. Because we cache data on a per-request basis, we create a new instance of Loader for each new request as needed.

API looks like:

export interface LoaderFactory<T, V> {
  name: string; // used to have a per-request cache of each loader type

  // when context is passed, there's potentially opportunities to batch data in the same
  // request
  // when no context is passed, no batching possible (except with explicit call to loadMany API)
  createLoader(context?: Context): Loader<T, V>;
}