Imagine the following query:
query {
user {
id
}
SomeOtherStuff(id: <--- I want to pass the id obtained from user) {
id
}
}
How do you pass a parameter obtained from one query to another ?
In GraphQL, fields at each "level" of the request are executed and resolved in parallel. In your example, user and SomeOtherStuff are both fields of the same type (the root Query type) -- so they will be resolved at the same time. That means each query essentially is not aware of the other or what the other resolved to.
You would have to handle this kind of scenario client side. In other words, request the user first, parse the response for the id and then make the second request.
Edit: In Apollo, you would utilize compose for this purpose:
const userQuery = gql`query User { user { id } }`;
const stuffQuery = gql`query SomeOtherStuff($id: ID) { someOtherStuff(id: $id){ stuff } }`;
export default compose(
graphql(userQuery, { name: 'userData' })
graphql(stuffQuery, { name: 'stuffData', options: ({userData:{id}={}}) => ({variables: {id}}) }),
)(YourComponent)
I agree with #DanielRearden. You should make type-resolvers so you can go infinitely deep into the graph. I made a simple server example here that shows deep relationships. Because all the noun-fields are references, it goes infinitely deep for any query.
With that server, you can run a query like this, for example:
{
hero {
name
friends {
name
friends {
name
friends {
name
friends: {
name
}
}
}
}
}
}
So, in your example, structure it like this:
query {
user {
id
otherStuff {
id
}
}
}
I was looking for same scenario and landed on this question. You can get it work other way around. It all depends how you have written your graphql resolver and you need to make sure that your database relations are intact. I have got it working like this.
Related
In my app every customer has a own table for its data. Depending on which customer was selected I want to dynamically build the tablename for the Graphql query.
For example:
// Query for customer 1
gql`
query overviewQuery {
customer_1 {
aggregate {
count
}
}
}
`
// Query for customer 2
gql`
query overviewQuery {
customer_2 {
aggregate {
count
}
}
}
`
I have the customer id in my vuex store and want to insert a variable into the query like in the following pseudocode which is not working.
const tblUserAggregateName = `customer_${this.$store.state.customer.customerId`
gql`
query overviewQuery {
${this.tblUserAggregateName} {
aggregate {
count
}
}
`
Is there an option how to do this or how can this problem be solved?
It is not an option to hardcode all different customer queries and selected them on runtime.
Thanks!
In the answers it was mentioned, that it is against best practice to dynamically change the table name of GraphQL queries.
As changing the complete database structure for all clients (they each have a separate Database with a own PostgreSQL schema name) is not an option, I found a solution the looks a little bit hacky and definitely not best practice but I thought I might be interesting to share for others with the same problem.
The approach is pretty easy: I write the query as a simple string where I could use variables and convert them later to the gql AST Object with graphql-tag
const query = () => {
const queryString = `
{
${customerId}_table_name {
aggregate {
count
}
}
}`
return gql`${queryString}`
}
Works, but I you have a better solution, I am happy to learn!
You can supply variables, but they should not be used to dynamically infer schema object names. This violates core concepts of GraphQL. Try this instead:
gql`
query overviewQuery ($customerId: ID!) {
customerData (id: $customerId) {
tableName
aggregate {
count
}
}
}`
Apollo provides great documentation on how to supply variables into a query here: https://www.apollographql.com/docs/react/data/queries/
The backend can then use the customerId to determine what table to query. The client making requests does not need to know (nor should it) where that data is or how it's stored. If the client must know the table name, you can add a field (as shown in the example)
I am trying to design a schema for an application and I have a problem that I can't solve. Here is a detail of the application
User A LIKES User B
User B MATCHS User B
Now User A and User B can start chatting with each others.
I also keep track of who visited each profile
User A VISITED BY User B
User A Visited BY User C
In the application, I have Me type with details of the user running the app. I have a me query that looks like this:
me {
id
name
email
...
...
likes { ## users who liked me
nextToken
edges {
node { ## user
id
name
...
}
}
}
matchs { ## users who matched with me
nextToken
edges {
node { ## user
id
name
...
...
}
}
}
Vists { ## users who visited me
nextToken
edges {
node { ##
id
name
...
...
}
}
}
}
In addition to that, I have listUsers query that list users nearby to Me and looks something like this:
listUsers {
nextToken
total
edges {
distance
node { ## user
id
name
...
...
}
}
}
MY QUESTION
Since there is a relationship between users (LIKED_BY, MATCHED_WITH) where do I use this relationship in my schema such that it is cashable. Keep in mind the relationship can change at the client from NO_RELATIONSHIP to LIKED_BY to MATCHED_WITH so if the relationship is duplicated in multiple places, this will be a problem.
I would really appreciate any help as I am out of ideas.
Thanks in advance.
In the GraphQL schema you'd generally make links like this explicit references to the other object.
type User {
id: ID!
...
matches: [User!] # actual users, not their IDs
likes: [User!]
visitedBy: [User!]
}
In your top-level Query type you can return the current user
type Query {
me: User
}
Now if I want the names and email addresses of people who have visited me, I can find out
query WhoVisitedMe {
me {
visitedBy { name, email }
}
}
You can traverse this graph, for example, to get recommendations: for people who visit you, who do they like?
query WhoDoVisitorsLike {
me {
visitedBy {
likes {
id
name
}
}
}
}
Your application's resolver code would need to fill in these object references.
You clarified in a comment:
While listing users in the search query, I need to be able to know the relationship between Me and the users
That is, you're trying to ask about some user
type User {
relationToMe: [RelationshipType!]
}
The relationToMe field can have any number (including zero) of relationship types; you can define those as a GraphQL enum
enum RelationshipType {
LIKES, LIKED_BY,
VISITED, VISITED_BY,
MATCHES # bidirectional
}
Then in your query you can ask
query FindSomeUsers($input: SearchUsersInput!) {
searchUsers(input: $input) {
users {
id, name, email
relationToMe
}
}
}
and get back a response like
{
"data": {
"searchUsers": {
"users": [
"id": "12345",
"name": "John Smith",
"email": "jsmith#example.com",
"relationToMe": ["VISITED", "MATCHES"]
]
}
}
You'd need to implement a custom resolver in your implementation to populate this field. If you had something like a many-to-many SQL join table, you could query that to fill in this field, if requested.
I'm trying to run a GraphQL query in the AWS AppSync console:
query MyQuery {
getUserInfoById(id: "1234566789") {
account {
id // need this value for getAvailableCourses
}
}
getAvailableCourses(accountId: "", pageNumber: 0) {
data {
id
name
type
}
}
}
Basically I need the value account.id in getUserInfoById for getAvailableCourses. I'm obviously new to GraphQL. How would I go about this?
To the best of my knowledge, there can be two ways you can do this.
You can handle this in your frontend by getting user's id
from the session info and pass it to the other query.
You can also merge these two queries and make it one. You will also have to change the respective fields. Then attach a resolver with AvailableCourses and use $ctx.source.id in the resolver to get further details. Schema would look something like this
type Account {
id : ID!
availableCourses: AvailableCourses
..
}
type AvailableCourses {
name: String!
type: String!
..
}
type Query {
getUserInfoById(id: ID!): Account
}
Using the returned fields as inputs for a second query into your datasource is precisely what field resolvers are for. I can't say for sure since I don't know your schema or access patterns but it looks like you need to make available courses a sub field of the user.
Imagine the following query:
query {
user {
id
}
SomeOtherStuff(id: <--- I want to pass the id obtained from user) {
id
}
}
How do you pass a parameter obtained from one query to another ?
In GraphQL, fields at each "level" of the request are executed and resolved in parallel. In your example, user and SomeOtherStuff are both fields of the same type (the root Query type) -- so they will be resolved at the same time. That means each query essentially is not aware of the other or what the other resolved to.
You would have to handle this kind of scenario client side. In other words, request the user first, parse the response for the id and then make the second request.
Edit: In Apollo, you would utilize compose for this purpose:
const userQuery = gql`query User { user { id } }`;
const stuffQuery = gql`query SomeOtherStuff($id: ID) { someOtherStuff(id: $id){ stuff } }`;
export default compose(
graphql(userQuery, { name: 'userData' })
graphql(stuffQuery, { name: 'stuffData', options: ({userData:{id}={}}) => ({variables: {id}}) }),
)(YourComponent)
I agree with #DanielRearden. You should make type-resolvers so you can go infinitely deep into the graph. I made a simple server example here that shows deep relationships. Because all the noun-fields are references, it goes infinitely deep for any query.
With that server, you can run a query like this, for example:
{
hero {
name
friends {
name
friends {
name
friends {
name
friends: {
name
}
}
}
}
}
}
So, in your example, structure it like this:
query {
user {
id
otherStuff {
id
}
}
}
I was looking for same scenario and landed on this question. You can get it work other way around. It all depends how you have written your graphql resolver and you need to make sure that your database relations are intact. I have got it working like this.
I learn to use GraphQL these days. In my opinion, To build a query, I need to build three parts:
Schema
type User{
id String
name String
cars [Car!]!
}
type Car{
id String
}
type Query{
user(id: String): User
}
DB Query function
{
user: async function ({id}) {
const user = await DB.user.findOne({id});
const userCars = await DB.car.find({userId: id});
user.cars = userCars;
return cars;
}
}
Client query
{
user (id: "1") {
name
cars {
id
}
}
}
That query returns a user's name and his cars. The DB query function always query for cars.
But sometimes I just need user's info:
{
user (id: "1") {
name
}
}
I don't want to query for cars, so I hope to make my DB query function can auto choose to query for cars or not.
How can I do this?
GraphQL.js will support either object properties or methods for resolver functions; this is discussed in its page on Object Types.
One way to deal with this is just to insert an anonymous function directly into the returned object:
{
user: async function ({id}) {
const user = await DB.user.findOne({id});
user.cars = () => DB.car.find({userId: id});
return cars;
}
}
Another is to create a wrapper object with a class that provides the id property and (asynchronous, lazy) cars method; some examples of this are in the GraphQL.js documentation. This approach tends to work in most GraphQL implementations in most languages.
I think you looking into auto-creating/mapping from GraphQL query into db query.
Every queries are db/project specific, so you should create this mapping. You can easily do that with graphql-fields package.
There is copy pasted WHY section from the package:
An underlying REST api may only return fields based on query params.
{
user {
profile {
firstName
},
id
}
}
should request /api/user?fields=profile,id
while
{
user {
email
}
}
should request /api/user?fields=email
Implement your resolve method like so:
resolve(root, args, context, info) {
const topLevelFields = Object.keys(graphqlFields(info));
return fetch(`/api/user?fields=${topLevelFields.join(',')}`);
}
It's best to avoid squeezing it all into one resolver function. Instead, create a separate ObjectType for Cars which has its own fields and its own resolver function. This way, the car query is only called if that field is requested.
In case you are using a RDS, join monster and data louder can help optimize performance of your queries.
Join Monster which relies on generating one big join query and also solve the problem of only requesting exactly the fields you need from the DB
Cached and Batched SQL Data Source which uses facebook's dataloader under the hood - it wont solve the problem of which fields to query (although the example uses knex, which will make that a lot easier), but instead it can cache and batch your queries