Radosław Miernik
Open source? Embrace, understand, develop.
Overfetching?
I have a bird for that!
Overfetching?
Someone fetches too much data.
REST
Almost
everyone.
GraphQL
?
Example
a.k.a. Story Time
Schema
type Post {
_id: ID!
views: Int!
}
type User {
_id: ID!
name: String!
posts: [Post!]!
totalViews: Int!
}
type Query {
users: [User!]!
}User.totalViews
is a sum of
Post.views
Resolvers
export const Query = {
users: async () =>
await getUsers()
};
export const User = {
posts: async ({ _id }) =>
await getPostsOf(_id),
totalViews: async ({ _id }) =>
sumViews(await getPostsOf(_id))
};Will it scale?
Resolvers v2
export const Query = {
users: async () =>
await getUsersWithTotalViews()
};
export const User = {
posts: async ({ _id }) =>
await getPostsOf(_id)
};Will it scale?
query {
users {
_id
}
}Resolvers are
overfetching!
Resolvers v3
export const Query = {
users: async (_, _, _, info) =>
includes(info, 'totalViews')
? await getUsersWithTotalViews()
: await getUsers()
};
export const User = {
posts: async ({ _id }) =>
await getPostsOf(_id)
};Will it scale?
Schema v2
type Post {
_id: ID!
likes: Int!
reach: Int!
views: Int!
}
type User {
_id: ID!
name: String!
posts: [Post!]!
totalLikes: Int!
totalReach: Int!
totalViews: Int!
}
type Query {
users: [User!]!
}User.total*
is a sum of
Post.*
Resolvers v4
export const Query = {
users: async (_, _, _, info) =>
includes(info, 'totalLikes')
? includes(info, 'totalReach')
? includes(info, 'totalViews')
? await getUsersWithLRV()
: await getUsersWithLR()
: includes(info, 'totalViews')
? await getUsersWithLV()
: await getUsersWithL()
: includes(info, 'totalReach')
? includes(info, 'totalViews')
? await getUsersWithRV()
: await getUsersWithR()
: includes(info, 'totalViews')
? await getUsersWithV()
: await getUsers()
};Will it scale?
DB
Code
Example
a.k.a. Story Time
AGAIN
Resolvers v5
import { astToOptions, astToPipeline }
from 'sparrowql-graphql';
const prepareOptions = () =>
// Use astToOptions!
// See docs!
export const Query = {
users: async (_, _, _, info) => {
const pipeline = astToPipeline(
info,
prepareOptions()
);
return await Users
.aggregate(pipeline)
.toArray();
}
};Will it scale?
DB
Code
FAQ
FAA
-
Only MongoDB.
-
Your DB schema has to be a DAG.
-
There's a detailed Medium article.
-
In production since April 2018.
That's all!
Overfetching? I have a bird for that!
By Radosław Miernik
Overfetching? I have a bird for that!
GraphQL Wroclaw #4
