How not to expose duplicated (normalize?) nodes via GraphQL? - optimization

Question

Given "user has many links" (what means a link was created by a user) DB entities relations, I want to develop API to fetch links along with users so that the returned data does not contain duplicated users.
In other words, instead of this request:
query {
links {
id
user {
id email
}
}
}
that returns the following data:
{
"data": {
"links": [
{
"id": 1,
"user": {
"id": 2,
"email": "user2#example.com"
}
},
{
"id": 2,
"user": {
"id": 2,
"email": "user2#example.com"
}
}
]
}
}
I want to make a request like this (note the "references" column):
query {
links {
id
userId
}
references {
users {
id
email
}
}
}
that returns associated users without duplicates:
{
"data": {
"links": [
{
"id": 1,
"userId": 2
},
{
"id": 2,
"userId": 2
},
],
"references": {
"users": [
{
"id": 2,
"email": "user2#example.com"
}
]
}
}
}
That should reduce amount of data transferred between client and server that adds a bit of speed boost.
Is there ready common implementation on any language of that idea? (Ideally, seeking for Ruby)

Answer 1

It's not a query or server role to normalize data.
there are no such possibilities in GraphQL specs;
server must return all asked fields within queried [response] structure;
... but you can implement some:
standarized (commonly used) pagination (relay style edges/nodes, nodes only or better both);
query [complexity] weights to promote this optimized querying style - separate problem;
reference dictionary field within queried type;
links {
egdes {
node {
id
title
url
authorId
# possible but limited usage with heavy weights
# author {
# id
# email
# }
}
}
pageInfo {
hasNextPages
}
referencedUsers {
id
email
}
}
where:
User has id and email props;
referencedUsers is [User!] type;
node.author is User type;
Normalizing Graphql client, like Apollo, can easily access cached user fields without making separate requests.
You can render (react?) some <User/> component (within <Link /> component) passing node.authorId as an argument like <User id={authorId} />. User component can useQuery hook with cache-only policy to read user props/fields.
See Apollo docs for details. You should implement this for yourself and document this to help/guide API users.