Can you limit an object to a maximum of 1 edge to another object?

Users Dgraph
,
#1

Example:
Two types of nodes, “Job” and “JobStatus”.
JobStatus stores information about a job’s status.
So it would be a 1 to 1 relationship.

  1. Is there any way to enforce a one to one relationship in the schema (graphQL/dgraph)?
  2. Is it possible to make it so each upsert/mutation of a Job’s jobStatus only modifies that one jobStatus (and doesn’t create another jobStatus) (without having to do uid shenanigans)?
#2

There is.

Example:

enum Tag {
    ...
}
type Post {
    ...
    // An array syntax signifies one to many relation,
    // so a Post can have as many tags as needed.
    tags: [Tag!]!
}

However, if you remove array syntax then:

enum Tag {
    ...
}
type Post {
    ...
    tags: Tag! // Non array syntax signifies, 1 to 1 relationship.
}

P.S. If I remember correctly, you can specify UID type as an Array in Ratel UI Schema.

3 Likes
#3

Oh thanks!
If I have a one to one relationship with another type

type Tag {
    ...
}
type Post {
    ...
    tag: Tag! // Non array syntax signifies, 1 to 1 relationship.
}

if I do a mutation of the Tag associated with Post, will the other Tag be overwritten, or will a new Tag be created and the old one will linger in the system

#4

Mutation means 3 operations, Create, Update & Delete.

Update will overwrite, Create will generate a new one and the old one will linger in the system.