TypeGraphQL-DataLoader

TypeGraphQL-DataLoader is an utility to use DataLoader with TypeGraphQL without fuss.

Install

``
npm install type-graphql-dataloader
`

The latest build is tested with the following packages:

- type-graphql 2.0.0
- apollo-server-express 4.4.1
- (optional) typeorm 0.3.17

Getting Started

Apollo Server is the first-class supported server. If your application uses Apollo Server, pass ApolloServerLoaderPlugin() as a plugin when instantiating the server. This plugin is for set-up and clean-up against each request.

`ts
import { ApolloServerLoaderPlugin } from "type-graphql-dataloader";
import { getConnection } from "typeorm";

...

const apollo = new ApolloServer({
schema,
plugins: [
ApolloServerLoaderPlugin({
typeormGetConnection: getConnection, // for use with TypeORM
}),
],
});

...
`

$3

TypeORM is the first-class supported ORM. If your application uses TypeORM with TypeGraphQL, adding @TypeormLoader decorator to relation properties will solve N + 1 problem. When the fields are accessed by graphQL, batch loading will be performed using DataLoader under the hood.

`ts
import { ObjectType, Field, ID } from "type-graphql";
import { TypeormLoader } from "type-graphql-dataloader";
import { Entity, PrimaryGeneratedColumn, ManyToOne, RelationId } from "typeorm";
import { User } from "./User";

@ObjectType()
@Entity()
export class Photo {
@Field((type) => ID)
@PrimaryGeneratedColumn()
id: number;

@Field((type) => User)
@ManyToOne((type) => User, (user) => user.photos)
@TypeormLoader()
user: User;
}
`

`ts
import { ObjectType, Field, ID } from "type-graphql";
import { TypeormLoader } from "type-graphql-dataloader";
import { Entity, PrimaryGeneratedColumn, OneToMany, RelationId } from "typeorm";
import { Photo } from "./Photo";

@ObjectType()
@Entity()
export class User {
@Field((type) => ID)
@PrimaryGeneratedColumn()
id: number;

@Field((type) => [Photo])
@OneToMany((type) => Photo, (photo) => photo.user)
@TypeormLoader()
photos: Photo[];
}
`

@TypeormLoader does not need arguments since v0.4.0. In order to pass foeign key explicitly, arguments are still supported. Take a look at previous README for details.

$3

It is possible to assign custom DataLoader to a field by adding @Loader decorator to the corresponding method with @FieldResolver. @Loader takes a batch load function which is passed to the DataLoader constructor. The decorated method should return a function which takes a DataLoader instance and returns Promise of loaded value(s).

`ts
import DataLoader from "dataloader";
import { groupBy } from "lodash";
import { Resolver, Query, FieldResolver, Root } from "type-graphql";
import { Loader } from "type-graphql-dataloader";
import { getRepository, In } from "typeorm";
import { Photo } from "./Photo";
import { User } from "./User";

@Resolver((of) => User)
export default class UserResolver {

...

@FieldResolver()
@Loader(async (ids, { context }) => { // batchLoadFn
const photos = await getRepository(Photo).find({
where: { user: { id: In([...ids]) } },
});
const photosById = groupBy(photos, "userId");
return ids.map((id) => photosById[id] ?? []);
})
photos(@Root() root: User) {
return (dataloader: DataLoader) =>
dataloader.load(root.id);
}
}
``