Removing nested entity

Users Dgraph
1

Suppose I have a Schema like:

type A {
  Id: ID
  propA: String
}

type B {
  Id: ID
  propB: String
  Links : [Link]
}

type Link {
  propLink : String
  propLink2 : String
  nestedA: A
}

So basically B can link to A’s but each link from B to A carries some extra properties.

I want to update one B and remove all of the links to As that it contains. I tried first setting its ‘Links’ property to an empty array, like so:

mutation MyMutation {
  updateB(input: {filter: {propB: {allofterms: "propB content"}}, set: {Links:[ ] }}) {
    B {
      Id
      Links {
        propLink
        propLink2
        A {
          Id
        }
      }
    }
  }
}

But all of the links are still there after this mutation. Then I tried passing the exact instance of an ‘A’ I’d like to remove:

mutation MyMutation {
  updateB(input: {filter: {propB: {allofterms: "propB content"}}, remove: {Links:[
{
  propLink : "prop1"
  propLink2: "prop2"
  A {
    Id: "0x4e12"

  }
}

 ] }}) {
    B {
      Id
      Links {
        propLink
        propLink2
        A {
          Id
        }
      }
    }
  }
}

And this responds with a panic:

{
  "errors": [
    {
      "message": "Internal Server Error - a panic was trapped.  This indicates a bug in the GraphQL server.  A stack trace was logged.  Please let us know by filing an issue with the stack trace."
    }
  ]
}

Whats the right way to do what I need? Is there a better schema def to achieve this? Does each Link property need to have its own ID?

2

Hi,
In order to update a nested predicate you should pass the whole object of B without A.
Your problem was that you pass only the empty links array

You can also use the remove keyword and set A to null like in the following example:

 name: "Update delete mutation with variables and null"
  gqlmutation: |
    mutation updatePost($patch: UpdatePostInput!) {
      updatePost(input: $patch) {
        post {
          postID
        }
      }
    }
  gqlvariables: |
    { "patch":
      { "filter": {
          "postID": ["0x123", "0x124"]
        },
        "remove": {
          "text": null
        }
      }
    }

Let me know if it works for you,
Or

1 Like
3

Hello, thanks for the reply.

First solution (pass the whole B obj on ‘set’ without the Links obj) does not result on a instance of B without Links (or an empty Links list which would also be ok).

Second suggestion (with variables and “remove” and to set to null) works!

Thank you!

4

If an empty list of links is ok you can pass the object B with an empty one.
The idea is that in order to updated a nested object you should pass it with its parent.

Great!

You’re welcome :slight_smile: