Namespace dgraph internal types

[abhimanyusinghgaur]

What version of Dgraph are you using?

latest:master

Have you tried reproducing the issue with the latest release?

Yes

What is the hardware spec (RAM, OS)?

doesn't matter

Steps to reproduce the issue (command/config used to run Dgraph).

• Run dgraph zero
• Run dgraph alpha --acl_secret_file ee/acl/hmac-secret (ACL enabled, this is just to get the ACL User groot inserted into Dgraph)
• Stop alpha instance
• Run dgraph alpha (Without ACL this time, so that we can make queries and mutations without token)
• Call /admin/schema with following POST body:

type  Device {
    uuid: String! @id @search(by: [hash])
    owner: User! @hasInverse(field: devices)
}

type User  {
    uuid: String! @id @search(by: [hash])
    devices: [Device] @hasInverse(field: owner)
}

2. Perform following GraphQL mutation (call graphql with given GraphQL body):

mutation {
  addDevice(input: [{
    uuid: "foo",
    owner: {
      uuid: "bar"
    }
  }]) {
    device {
      uuid
      owner {
        uuid
      }
    }
  }
}

3. Device gets added successfully, fine.
4. Now, perform following GraphQL query:

query {
  queryUser(filter: null) {
    uuid
    devices {
      uuid
    }
  }
}

Expected behaviour and actual result.

• Expected Behaviour:

{
  "data": {
    "queryUser": [
      {
        "uuid": "bar",
        "devices": [
          {
            "uuid": "foo"
          }
        ]
      }
    ]
  }
}

• Actual Result:

{
  "errors": [
    {
      "message": "Non-nullable field 'uuid' (type String!) was not present in result from Dgraph.  GraphQL error propagation triggered.",
      "locations": [
        {
          "line": 3,
          "column": 5
        }
      ],
      "path": [
        "queryUser",
        1,
        "uuid"
      ]
    }
  ],
  "data": {
    "queryUser": [
      {
        "uuid": "bar",
        "devices": [
          {
            "uuid": "foo"
          }
        ]
      },
      null
    ]
  }
}

Analysis

As a GraphQL user, I just declared some types, one of them (type User) happens to have same name as dgraph's internal type for ACL user. This causes a problem, as to how to identify which nodes are associated with user declared types and which ones with internal types. As a result, the actual results above contain errors, along with a null user in data.
If you call /query with following body, then you can see the reason why this happens:

query {
    q1(func: eq(dgraph.type, "User")) {
    	uid
    	dgraph.xid
    	expand(_all_) {
	    	expand(_all_)
    	}
    }
  }

following results are returned:

{
    "data": {
        "q1": [
            {
                "uid": "0x3",
                "User.uuid": "bar",
                "User.devices": [
                    {
                        "Device.uuid": "foo"
                    }
                ]
            },
            {
                "uid": "0x5",
                "dgraph.xid": "groot"
            }
        ]
    },
    "extensions": {
        "server_latency": {
            "parsing_ns": 79899,
            "processing_ns": 2018313,
            "encoding_ns": 28383,
            "assign_timestamp_ns": 547917,
            "total_ns": 2755443
        },
        "txn": {
            "start_ts": 25
        },
        "metrics": {
            "num_uids": {
                "Device.owner": 1,
                "Device.uuid": 1,
                "User.devices": 2,
                "User.uuid": 2,
                "dgraph.type": 0,
                "dgraph.xid": 2,
                "uid": 2
            }
        }
    }
}

As groot is also a User, so it is also returned by dgraph in response to query, although, groot was never inserted by us, as it got inserted by ACL instance.

So, any types which are used by dgraph internally should be namespaced, in order to avoid collision with user declared types. For example, ACL User can be __User or dgraph.User, or something like that.