I'm trying to figure out cascade deletion in GraphQL.
I'm attempting to delete a node of type Question, but type QuestionVote has a required relation to Question. I'm looking for a way to delete a Question and all its votes at once.
Mutation for deleting a Question:
type Mutation {
deleteQuestion(where: QuestionWhereUniqueInput!): Question!
}
And its resolver (I'm using Prisma):
function deleteQuestion(parent, args, context, info) {
const userId = getUserId(context)
return context.db.mutation.deleteQuestion(
{
where: {id: args.id}
},
info,
)
}
How can I modify that mutation to also delete related QuestionVote nodes? Or should I add a separate mutation that deletes one or multiple instances of QuestionVote?
In case it's important, here are the mutations that create Question and QuestionVote:
function createQuestion(parent, args, context, info) {
const userId = getUserId(context)
return context.db.mutation.createQuestion(
{
data: {
content: args.content,
postedBy: { connect: { id: userId } },
},
},
info,
)
}
async function voteOnQuestion(parent, args, context, info) {
const userId = getUserId(context)
const questionExists = await context.db.exists.QuestionVote({
user: { id: userId },
question: { id: args.questionId },
})
if (questionExists) {
throw new Error(`Already voted for question: ${args.questionId}`)
}
return context.db.mutation.createQuestionVote(
{
data: {
user: { connect: { id: userId } },
question: { connect: { id: args.questionId } },
},
},
info,
)
}
Thanks!
You can set up cascade deletion by modifying your datamodel.
Given your question, I assume your datamodel looks somewhat like this:
type Question {
id: ID! #unique
votes: [QuestionVote!]! #relation(name: "QuestionVotes")
text: String!
}
type QuestionVote {
id: ID! #unique
question: Question #relation(name: "QuestionVotes")
isUpvote: Boolean!
}
Then you have to add the onCascade: DELETE field to the #relation directive like so:
type Question {
id: ID! #unique
votes: [QuestionVote!]! #relation(name: "QuestionVotes" onDelete: CASCADE)
text: String!
}
type QuestionVote {
id: ID! #unique
question: Question #relation(name: "QuestionVotes")
isUpvote: Boolean!
}
Now, every time a Question node is deleted, all related QuestionVote nodes are also deleted.
Note: If omitting onDelete, the value is automatically set to onDelete: SET_NULL by default. This means that deleting a node results in setting the other side of the relation to null.
You can read more about cascading deletes in Prisma in the documentation.
Related
I have begun testing out prisma 2 and graphql in general for a new application. I am running into an issue with an explicit many to many table on being able to query relations.
Here is my apollo schema:
scalar DateTime
type Query {
user(id: String!): User
users: [User]
spaces: [Space]
roles: [Role]
}
type Mutation {
createUser(id: String!, email: String!): User!
createSpace(name: String!): Space!
}
type User {
id: ID!
email: String!
spaces: [UserSpace!]
createdAt: DateTime!
updatedAt: DateTime!
}
type Space {
id: ID!
name: String!
users: [UserSpace!]
createdAt: DateTime!
updatedAt: DateTime!
}
type Role {
id: ID!
name: String!
description: String!
users: UserSpace
createdAt: DateTime!
updatedAt: DateTime!
}
type UserSpace {
id: ID!
user: User!
space: Space!
role: Role!
createdAt: DateTime!
updatedAt: DateTime!
}
Here is my prisma schema:
// This is your Prisma schema file,
// learn more about it in the docs: https://pris.ly/d/prisma-schema
// npx prisma migrate dev
// npx prisma generate
datasource db {
provider = "postgresql"
url = env("DATABASE_URL")
}
generator client {
provider = "prisma-client-js"
}
model User {
id String #id
email String #unique
spaces UserSpace[]
createdAt DateTime #default(now())
updatedAt DateTime #updatedAt
}
model Space {
id Int #default(autoincrement()) #id
name String #unique
users UserSpace[]
createdAt DateTime #default(now())
updatedAt DateTime #updatedAt
}
model Role {
id Int #default(autoincrement()) #id
name String #unique
description String
users UserSpace[]
createdAt DateTime #default(now())
updatedAt DateTime #updatedAt
}
model UserSpace {
id Int #default(autoincrement()) #id
user User #relation(fields: [userId], references: [id])
userId String
space Space #relation(fields: [spaceId], references: [id])
spaceId Int
role Role #relation(fields: [roleId], references: [id])
roleId Int
createdAt DateTime #default(now())
updatedAt DateTime #updatedAt
}
Here is my mutations resolver:
const { prisma } = require(".prisma/client");
async function createUser(parent, args, context, info) {
return await context.prisma.user.create({
data: {
...args,
},
});
}
async function createSpace(parent, args, context, info) {
const isAuthenticated = context.authentication.isAuthenticated;
let role = null;
if(!isAuthenticated) {
throw new Error("Not Authenticated");
}
try {
role = await context.prisma.role.findUnique({
where: {
name: "Space Administrator",
},
});
}
catch(err) {
throw new Error(err);
}
return await context.prisma.space.create({
data: {
...args,
users: {
create: {
role: {
connect: { id: role.id },
},
user: {
connect: { id: context.authentication.auth0Id },
},
},
},
},
});
}
module.exports = {
createUser,
createSpace,
}
Here is my user resolver (I know this is where the problem is however I do not know how to solve the issue):
function spaces(parent, args, context, info) {
return context.prisma.user.findUnique({ where: { id: parent.id } }).spaces();
}
module.exports = {
spaces,
}
Basically when I create the space the user is added as a Space Administrator to the space and then should be able to be queried with the following:
query {
users {
id
email
spaces {
id
role {
name
}
space {
name
}
}
createdAt
}
}
However when I run the query I get the following error:
"message": "Cannot return null for non-nullable field UserSpace.role.",
How in prisma 2 do I make the resolver for the users work with an explicit many to many table and how it has the third relation in there? I am new to prisma and graphql so if there anything else that stands out also I would like to have the input.
I'm using the word type to refer to object-models in your GraphQL schema and model to refer to data-models in your Prisma Schema.
The Problem
I see that you have a User type resolver, that has a resolver function for User.spaces field in your User type. The query that you have defined in your User.spaces resolver will return the relevant userSpace records from the database.
However, these userSpace records do not by default resolve the role field, as it is a relation field. This is how prisma works (relation fields are not resolved by default, unless explicitly stated).
Solution
Create a resolver for the UserSpace type and explicitly define the the resolver function for UserSpace.role field. This is what it will look like
// UserSpace resolver module
function role(parent, args, context, info) {
return context.prisma.userSpace.findUnique({ where: { id: parent.id } }).role();
}
module.exports = {
role,
}
While there are some other ways to solve this problem, the way I have shown (along with the specific syntax) is recommended because under the hood it allows prisma to perform certain optimizations to solve the n+1 query problem. But, if you don't know what that is, you don't necessarily need to worry about it either.
Did you provide the value to users arg? like this: users(id: "string_value"). Because is id is required.
I want to alter the mutation using Laravel Creating event. I want to fetch task ID from key that is coming from front end. And then i want to add this ID in replace of key so that my task will be create automatically using lighthouse structure. Here is sample mutation
mutation
{
createUser(input: {
firstname: "last"
email: "abc#gmaiol.com"
task:
{
create: {
key: 'reminder'
}
}
})
{
id
}
}
My recommendation is to create a resolver for your specific situation:
mutation
{
createUser(input: {firstname: "last", email: "abc#gmaiol.com", key: "reminder"})
{
id
}
}
Remember to always use double quotes " ", never use single quotes ' '
In your schema.graphql
input newUser {
firstname: String!
email: String!
key: String!
}
type newUserResponse {
ID: ID!
}
createUser(data: newUser): newUserResponse #field(resolver: "App\\GraphQL\\Mutations\\createUser")
Here's an example of the resolver: Resolver example
Also check the docs: https://lighthouse-php.com/4.9/api-reference/resolvers.html
Within my resolver I seem to be unable to fetch connected data
this works in the graphql playground (prisma) but I am unsure of the syntax about how to form a resolver in apollo server
// my typedef for activity is
type Activity {
id: ID! #id
ActivityType: ActivityType!
title: String!
date: DateTime
user: User!
distance: Float!
distance_unit: Unit!
duration: Float!
elevation: Float
elevation_unit: Unit
createdAt: DateTime! #createdAt
updatedAt: DateTime! #updatedAt
// and my resolver currently looks like this
async activity(parent, args, ctx, info) {
const foundActivity = await ctx.db.query.activity({
where: {
id: args.id
}
});
// todo fetch user data from query
console.log(foundActivity);
}
// where db has been placed onto the ctx (context)
// the CL gives all of the data for Activity apart from the user
// in the playground I would do something like this
query activity {
activity(where: {
id: "cjxxow7c8si4o0b5314f9ibek"
}){
title
user {
id
name
}
}
}
// but I do not know how to specify what is returned in my resolver.
console.log(foundActivity) gives:
{ id: 'cjxxpuh1bsq750b53psd2c77d',
ActivityType: 'CYCLING',
title: 'Test Activity',
date: '2019-07-10T20:21:27.681Z',
distance: 13.4,
distance_unit: 'KM',
duration: 90030,
elevation: 930,
elevation_unit: 'METERS',
createdAt: '2019-07-10T20:48:50.879Z',
updatedAt: '2019-07-10T20:48:50.879Z' }
Prisma is the DB ORM and then I have an Apollo-Server 2 server running on top of that. Unfortunately, stack overflow also thinks that there is too much code on this post so I will have to waffle on about inconsequential gibberish due to the fact that their system can't handle it.
You will have to implement a resolver for Activity.user. Unfortunately your entity does not seem to contain a reference to the user. First, add the user connection to your Prisma data model. Then implement a resolver for Activity.user. I am not very familiar with Prisma 1 but this naive implementation should already do what you want:
let resolvers = {
Query: {
// ...
},
Activity: {
user(parent, args, ctx) {
return ctx.db.query.activity({ id: parent.id }).user();
}
}
}
Find out more about resolving relations in Prisma here
So the answer was incredibly simple:
I just add a second argument to the query (after the "where" with a gql tag of the data shape to be returned so my code now looks like:
const foundActivity = await ctx.db.query.activity(
{
where: {
id: args.id
}
},
`{id title user { id name }}`
);
Let's take an example from the github repo of prisma:
We have a user, the user could have multiple posts, and one post could have multiple links.
My goal is, to retrieve all posts and all links.
This means, my response is a list (links) in a list (posts).
I want to map the values I get back as two nested lists.
datamodel.prisma
type User {
id: ID! #id
email: String! #unique
name: String
posts: [Post]!
}
type Post {
id: ID! #id
createdAt: DateTime! #createdAt
updatedAt: DateTime! #updatedAt
published: Boolean! #default(value: false)
title: String!
content: String
author: User!
links: [Link]!
}
type Link {
id: ID! #id
url: String
title: String
post: Post!
}
schema.graphql
type Query {
...
}
type Mutation {
...
}
type Link {
id: ID!
url: String
title: String
post: Post!
}
type Post {
id: ID!
createdAt: DateTime!
updatedAt: DateTime!
published: Boolean!
title: String!
content: String
author: User!
}
type User {
id: ID!
email: String!
name: String
posts: [Post]!
}
I want to query all posts of a user, and all of the links for every post in the response.
How would I query this request?
user {
id
posts {
id
links {
id
}
}
}
The above code snipper would not work.
EDIT
I want to use the following:
User: {
listPosts: (parent, args, context, info) {
return context.prisma.posts().links()
}
}
So in my response (data in front-end via react-apollo Query Component), I want to map over posts AND the links in each post.
BUT the links attribute in posts is null.
Is there another way to achieve this?!
According to the docs:
Prisma client has a fluent API to query relations in your database. Meaning you can simply chain your method calls to navigate the relation properties of the returned records. This is only possible when retrieving single records, not for lists. Meaning you can not query relation fields of records that are returned in a list.
In order to get around that limitation, you can use the $fragment method:
const fragment = `
fragment UserWithPostsAndLinks on User {
id
email
name
posts {
id
title
content
links {
id
url
title
}
}
}
`
const userWithPostsAndLinks = await prisma.user({ id: args.id }).$fragment(fragment)
So, I'm testing subscriptions on Graphcool and would appreciate some clarification on how exactly they work.
I have a one to many relationship from Posts on Comments:
Schema
type Posts {
caption: String!
comments: [Comments!]! #relation(name: "PostsOnComments")
createdAt: DateTime!
displaysrc: String!
id: ID!
likes: Int
updatedAt: DateTime!
}
type Comments {
createdAt: DateTime!
id: ID!
posts: Posts #relation(name: "PostsOnComments")
text: String!
updatedAt: DateTime!
user: String!
}
The subscription I run in Graphcool is as follows:
subscription CreatedDeletedComments {
Comments(
filter: {
mutation_in: [CREATED, DELETED]
}
) {
mutation
node {
id
user
text
}
}
}
If I run the following in my React app, a created notification is fired:
return this.props.client.mutate({
mutation: gql`
mutation createComment ($id: ID, $textVal: String!, $userVal: String!) {
createComments (postsId: $id, text: $textVal, user: $userVal){
id
text
user
}
}
`,
variables: {
"id": postID,
"textVal": textVal,
"userVal": userVal
},
// forceFetch: true,
})
But if I run the following, no deleted notification is fired:
return this.props.client.mutate({
mutation: gql`
mutation removeComment ($id: ID!, $cid: ID!) {
removeFromPostsOnComments (postsPostsId: $id, commentsCommentsId: $cid){
postsPosts {
id
displaysrc
likes
comments {
id
text
user
}
}
}
}
`,
variables: {
"id": postID,
"cid": commentID
},
// forceFetch: true,
})
What am I overlooking here?
With the subscription
subscription CreatedDeletedComments {
Comments(
filter: {
mutation_in: [CREATED, DELETED]
}
) {
mutation
node {
id
user
text
}
}
}
you are subscribing to comment nodes being created or deleted. However, with the mutation removeFromPostsOnComments, you are not deleting any comment nodes. Instead, you are only deleting the connection between a post and a comment.
You can adjust your mutation request to delete the comment entirely instead of disconnecting it from the post:
return this.props.client.mutate({
mutation: gql`
mutation removeComment ($cid: ID!) {
deleteComment(id: $cid) {
id
}
}
`,
variables: {
"cid": commentID
},
// forceFetch: true,
})
If you don't want to delete the comment entirely but still want to hide it in your app, you could have a boolean field deleted that acts as a soft deletion marker.
Then you could subscribe to UPDATED comments instead of DELETED comments and check if the field deleted was updated. Refer to the
docs for more information on how to do that with updatedFields.
Subscriptions for relations is also already part of our roadmap.