Eager Loader for @nestjs/graphql
This package provides support for eager loading of relations in GraphQL queries, allowing you to significantly reduce the number of database queries required to fetch related data. With this package, you can easily define which relations should be eager-loaded for each GraphQL resolver, and the package takes care of the rest.
It utilises @sapientpro/typeorm-eager-load package to load relations. Please refer to the documentation of that package for more information.
Installation
Install the package using npm:
npm install @sapientpro/nestjs-graphql-eager-load --save
Install the package using yarn:
yarn add @sapientpro/nestjs-graphql-eager-load
Configure graphql schema in your application:
import { eagerLoadSchemaTransformer } from '@sapientpro/nestjs-graphql-eager-load';
@Module({
imports: [
GraphQLModule.forRoot<ApolloDriverConfig>({
...
transformSchema: eagerLoadSchemaTransformer,
}),
],
})Usage
Import the EagerLoad directive from the nestjs-graphql-eager-load package:
import { EagerLoad } from '@sapientpro/nestjs-graphql-eager-load';Then, use it to load entity relations:
import { EagerLoad } from "@sapientpro/nestjs-graphql-eager-load";
@ObjectType()
class Article {
@Field(() => [Comment])
@EagerLoad()
comments: Comment[];
@ResolveField(() => [Tag])
@EagerLoad(['tags'])
tags(@Root() article: Article): TagEntity[] {
return article.tags;
}
}Relation Definition
You can also use a relation definition like in @sapientpro/typeorm-eager-load package. Please refer to the documentation of that package for more information.
@EagerLoad({
comments: (builder) => {
//some constraints
}
})If you use only one relation that equals the field name you can specify only constraint function.
@Field(() => [Comment])
@EagerLoad((builder) => {
//some constraints
})
comments: Comment[];PassTrough
If you have a nested model with same entity you can specify passTrough option to pass the processing to the nested model.
@EagerLoad(true)
@ResolveField(() => ArticleMeta)
meta(@Root() article: ArticleEntity): ArticleEntity {
return article;
}Arguments
If you need to use arguments to load relations. You can use the third argument in your constraint function in this case.
@EagerLoad({
comments: (builder, {}, args) => {
if(args.newerThan) {
builder.where('comments.createdAt >= :date', {date: args.newerThan});
}
}
})
@ResolveFioeld(() => [Comment])
comments(@Root() article: Article, @Args() args: CommentsArgs): CommentEntity[] {
return article.comments;
}GraphQL context
If you need to use context in your constraint function, you can use the fourth argument in your constraint function.
@EagerLoad({
comments: (builder, {}, args, context) => {
if(args.onlyMyComments) {
builder.where('comments.authorId = :userId', {userId: context.req.user.id});
}
}
})
@ResolveField(() => [Comment])
comments(@Root() article: Article, @Args() args: CommentsArgs): CommentEntity[] {
return article.comments;
}EagerLoadEntry
If you have a field resolver that is not a query or mutation, you can mark it as LoadEagerEntry to enable eager load processing
@EagerLoadEntry()
@ResolveField(() => [Comment])
comments(): CommentEntity[] {
return commentsRepository.findAll();
}also you can specify field to use as entity entry
@EagerLoadEntry('nodes')
@ResolveField(() => PaginatedComment)
comments(): CommentEntity[] {
return {
nodes: commentsRepository.findAll()
};
}Contributing
Contributions are welcome! If you have any bug reports, feature requests, or patches, please open an issue or create a pull request.
License
This package is licensed under the MIT License.