Graphcool (Graphql): how to make exact filter in array of Id - filtering

Question

I have chat model
type Chat #model {
id: ID! #isUnique
name: String
messages: [Message!]! #relation(name: "ChatMessages")
users: [User!]! #relation(name: "ChatUser")
createdAt: DateTime!
}
And I've created a chat with two people ["123", "234"] and all was ok. But when I want to create a new group chat with three people where two of them already have a chat with themselves ["123", "234", "345"]
I make a query for check is this chat exist with three people
query {
allChats(filter:{
users_every: {
id_in: ["123", "234", "345"]
}
}
){
id
users{
id
}
}
}
and I got response that this chat already exist, but here I have just two users not all of them
{
"data": {
"allChats": [
{
"id": "cjgxuub2351uj0187qeil548m",
"users": [
{
"id": "123"
},
{
"id": "234"
}
]
}
]
}
}

Answer 1

The every suffix in users_every makes sure it matches all chats that have only users with ids from the id_in array. That's why you're getting chats with fewer users, because subsets match.
The solution:
query {
allChats(
filter: {
AND: [
{ users_some: { id: "123" } },
{ users_some: { id: "234" } },
{ users_some: { id: "345" } },
{ users_every: { id_not_in: ["678", "910", ...] } }
]
}
) {
id
users {
id
}
}
}
The users_some filters make sure to select chats that have at least all those 3 users attached. The users_every - id_not_in is needed to exclude the chats with those three plus any other users.
In all honesty this seems a bit convoluted to me, and probably kinda unfeasible for an app with a large number of users. I'd love for graph.cool to implement some easier solution in the api.
As an alternative, you could just omit the users_every filter, and then, in your client app, pick from the results only the chat that has exactly 3 users.