Вот как правильно юзать DataLoader
js
const ArticleType = new GraphQLObjectType({
name: 'Article',
fields: () => ({
title: { type: GraphQLString },
authorId: { type: GraphQLString },
author: {
type: AuthorType,
// WAS
// resolve: source => {
// return authorModel.findById(source.authorId);
// },
// BECAME:
resolve: (source, args, context, info) => {
// See dl-server.js, there was created context = { dataloaders: new WeakMap() };
const { dataloaders } = context;
// init DataLoader once, if not exists
// we use a MAGIC here
// `Set.get(info.fieldNodes)` is unique for every field in the query
// it helps to determine the same resolvers
let dl = dataloaders.get(info.fieldNodes);
if (!dl) {
dl = new DataLoader(async (ids: any) => {
// regular request to our database
const rows = await authorModel.findByIds(ids);
// IMPORTANT: we MUST return rows in the same order like we get ids
const sortedInIdsOrder = ids.map(id => rows.find(x => x.id === id));
return sortedInIdsOrder;
});
dataloaders.set(info.fieldNodes, dl);
}
// load author via dataloader
return dl.load(source.authorId);
},
},
}),
});
