Is there a standard way to send a dynamic number of mutations in the same request with Apollo client ?
I have to deal with a Graphql API that only expose a single delete mutation, and I'd like to call it with multiple ids. Here's how it's defined:
mutation DeleteItemById($id: Int) {
delete_item(id: $id) {
id
}
}
From what I read, I could do something like
mutation DeleteItemById($id_1: Int, $id_2: Int) {
delete_item_1: delete_item(id: $id_1) {
id
}
delete_item_2: delete_item(id: $id_2) {
id
}
}
But how could I generate such a query dynamically ? Is it a good practice anyway ? I always read it was not a good idea to dynamically generate graphql queries.
Plus, I'm using graphql-codegen and statically defining queries in .graphql files, so I imagine it will have trouble parsing dynamic ones.
In general it's a bad idea to generate GraphQL queries dynamically. A good way to deal with this is to create a new mutation that supports multiple ids, validate and delete all in the same batch, like:
type Mutation {
deleteItems(ids: [String!]!): Boolean!
}
Related
Let's say my graphql server wants to fetch the following data as JSON where person3 and person5 are some id's:
"persons": {
"person3": {
"id": "person3",
"name": "Mike"
},
"person5": {
"id": "person5",
"name": "Lisa"
}
}
Question: How to create the schema type definition with apollo?
The keys person3 and person5 here are dynamically generated depending on my query (i.e. the area used in the query). So at another time I might get person1, person2, person3 returned.
As you see persons is not an Iterable, so the following won't work as a graphql type definition I did with apollo:
type Person {
id: String
name: String
}
type Query {
persons(area: String): [Person]
}
The keys in the persons object may always be different.
One solution of course would be to transform the incoming JSON data to use an array for persons, but is there no way to work with the data as such?
GraphQL relies on both the server and the client knowing ahead of time what fields are available available for each type. In some cases, the client can discover those fields (via introspection), but for the server, they always need to be known ahead of time. So to somehow dynamically generate those fields based on the returned data is not really possible.
You could utilize a custom JSON scalar (graphql-type-json module) and return that for your query:
type Query {
persons(area: String): JSON
}
By utilizing JSON, you bypass the requirement for the returned data to fit any specific structure, so you can send back whatever you want as long it's properly formatted JSON.
Of course, there's significant disadvantages in doing this. For example, you lose the safety net provided by the type(s) you would have previously used (literally any structure could be returned, and if you're returning the wrong one, you won't find out about it until the client tries to use it and fails). You also lose the ability to use resolvers for any fields within the returned data.
But... your funeral :)
As an aside, I would consider flattening out the data into an array (like you suggested in your question) before sending it back to the client. If you're writing the client code, and working with a dynamically-sized list of customers, chances are an array will be much easier to work with rather than an object keyed by id. If you're using React, for example, and displaying a component for each customer, you'll end up converting that object to an array to map it anyway. In designing your API, I would make client usability a higher consideration than avoiding additional processing of your data.
You can write your own GraphQLScalarType and precisely describe your object and your dynamic keys, what you allow and what you do not allow or transform.
See https://graphql.org/graphql-js/type/#graphqlscalartype
You can have a look at taion/graphql-type-json where he creates a Scalar that allows and transforms any kind of content:
https://github.com/taion/graphql-type-json/blob/master/src/index.js
I had a similar problem with dynamic keys in a schema, and ended up going with a solution like this:
query lookupPersons {
persons {
personKeys
person3: personValue(key: "person3") {
id
name
}
}
}
returns:
{
data: {
persons: {
personKeys: ["person1", "person2", "person3"]
person3: {
id: "person3"
name: "Mike"
}
}
}
}
by shifting the complexity to the query, it simplifies the response shape.
the advantage compared to the JSON approach is it doesn't need any deserialisation from the client
Additional info for Venryx: a possible schema to fit my query looks like this:
type Person {
id: String
name: String
}
type PersonsResult {
personKeys: [String]
personValue(key: String): Person
}
type Query {
persons(area: String): PersonsResult
}
As an aside, if your data set for persons gets large enough, you're going to probably want pagination on personKeys as well, at which point, you should look into https://relay.dev/graphql/connections.htm
I have a mutation:
const createSomethingMutation = gql`
mutation($data: SomethingCreateInput!) {
createSomething(data: $data) {
something {
id
name
}
}
}
`;
How do I create many Somethings in one request? Do I need to create a new Mutation on my GraphQL server like this:
mutation {
addManySomethings(data: [SomethingCreateInput]): [Something]
}
Or is there a way to use the one existing createSomethingMutation from Apollo Client multiple times with different arguments in one request?
You can in fact do this using aliases, and separate variables for each alias:
const createSomethingMutation = gql`
mutation($dataA: SomethingCreateInput!) {
createA: createSomething(data: $dataA) {
something {
id
name
}
}
createB: createSomething(data: $dataB) {
something {
id
name
}
}
}
`;
You can see more examples of aliases in the spec.
Then you just need to provide a variables object with two properties -- dataA and dataB. Things can get pretty messy if you need the number of mutations to be dynamic, though. Generally, in cases like this it's probably easier (and more efficient) to just expose a single mutation to handle creating/updating one or more instances of a model.
If you're trying to reduce the number of network requests from the client to server, you could also look into query batching.
It's not possible so easily.
Because the mutation has one consistent name and graphql will not allow to have the same operation multiple times in one query. So for this to work Apollo would have to map the mutations into aliases and then even map the variables data into some unknown iterable form, which i highly doubt it does.
How would you use graphQL to query by a "relational" entity value?
For instance, lets say we have a bunch of person-objects. Each "person" then has a relation to an interest/hobby which then has a property called "name".
Now lets say that we want to query for the name of each person with a specific interest, how would such a query be "conducted" using GraphQL?
Using OData it would be something like Persons?$select=name&$expand(Interests($filter=name eq 'Surfing')).. what would be the equivalent for GraphQL?
There is no one equivalent. With the exception of introspection, the GraphQL specification does not dictate what types a schema should have, what fields it should expose or what arguments those fields should take. In other words, there is no one way to query relationships or do things like filtering, sorting or pagination. If you use Relay, it has its own spec with a bit more guidance around things like pagination and connections between different nodes, but even Relay is agnostic to filtering. It's up to the individual service to decide how to implement these features.
As an example, if we set up a Graphcool or Prisma server, our query might look something like this:
query {
persons(where: {
interest: {
name: "Surfing"
}
}) {
name
}
}
A query to a Hasura server might look like this:
query {
persons(where: {
interest: {
name: {
_eq: "Surfing"
}
}
}) {
name
}
}
But there's nothing stopping you from creating a schema that would support a query like:
query {
persons(interest: "Surfing") {
name
}
}
I'd like to resolve a field called 'outstandingBalance' in Client type. If front-end query:
query {
Client {
id
name
outstandingBalance
}
}
The resolver function for outstandingBalance is expensive to run. If front-end query:
query {
Client {
id
name
}
}
Then, don't trigger the resolver for 'outstandingBalance'. I have basic understanding of graphql and read most of its official document. But have not seen an answer to this pattern, or this way of using Graphql is not allowed?
Question
Is there a thing called "Nont-root level resolver" for graphql? like the 'outstandingBalance' field in Client type?
Question: How to implement in graphql? Especially using resolver:
async function outstandingBalance(obj, args, context, info) {
console.log('called...')
}
to query one field in one type based on if this field is queried?
Graphql is great and I've started using it in my app. I have a page that displays summary information and I need graphql to return aggregate counts? Can this be done?
You would define a new GraphQL type that is an object that contains a list and a number. The number would be defined by a resolver function.
On your GraphQL server you can define the resolver function and as part of that, you would have to write the code that performs whatever calculations and queries are necessary to get the aggregate counts.
This is similar to how you would write an object serializer for a REST API or a custom REST API endpoint that runs whatever database queries are needed to calculate the aggregate counts.
GraphQL's strength is that it gives the frontend more power in determining what data specifically is returned. Some of what you write in GraphQL will be the same as what you would write for a REST API.
There's no automatic aggregate function in GraphQL itself.
You can add a field called summary, and in the resolve function calculate the totals.
You should define a Type of aggregated data in Graphql and a function you want to implement it. For example, if you want to write the following query:
SELECT age, sum(score) from student group by age;
You should define the data type that you want to return:
type StudentScoreByAge{
age: Int
sumOfScore: Float
}
and a Graphql function:
getStudentScoreByAge : [StudentScoreByAge]
async function(){
const res = await client.query("SELECT age, sum(score) as sumOfScore
from Student group by age");
return res.rows;
}
... need graphql to return aggregate counts? Can this be done?
Yes, it can be done.
Does GraphQL does it automatically for you? No, because it does not know / care about where you get your data source.
How? GraphQL does not dictate how you get / mutate the data that the user has queried. It's up to your implementation to get the requested aggregated data. You could get aggregated data directly from your MongoDB and serve it back, or you get all the data you need from your data source and do the aggregation yourself.
If you are using Hasura, in the explorer, you can definitely see an "agregate" table name, thus, your query would look something similar to the following:
query queryTable {
table_name {
field1
field2
}
table_name_aggregate {
aggregate { count }
}
}
In your results, you will see the total row count for the query
"table_name_aggregate": {
"aggregate": {
"count": 9973
}
This depends on whether you build the aggregator into your schema and are able to resolve the field.
Can you share what kind of GraphQL Server you're running? As different languages have different implementations, as well as different services (like Hasura, 8base, and Prisma).
Also, when you say "counts", I'm imagining a count of objects in a relation. Such as:
query {
user(id: "1") {
name
summaries {
count
}
}
}
// returns
{
"data": {
"user": {
"name": "Steve",
"summaries": {
"count": 10
}
}
}
}
8base provides the count aggregate by default on relational queries.