Triples - Mutations

Documentation
1

A mutation that adds triples is done with the set keyword.

{
  set {
    # triples in here
  }
}

The input language is triples in the W3C standard RDF N-Quad format.

Each triple has the form

<subject> <predicate> <object> .

Meaning that the graph node identified by subject is linked to object with directed edge predicate. Each triple ends with a period. The subject of a triple is always a node in the graph, while the object may be a node or a value (a literal).

For example, the triple

<0x01> <name> "Alice" .
<0x01> <dgraph.type> "Person" .

Represents that graph node with ID 0x01 has a name with string value "Alice". While triple

<0x01> <friend> <0x02> .

Represents that graph node with ID 0x01 is linked with the friend edge to node 0x02.

Dgraph creates a unique 64 bit identifier for every blank node in the mutation - the node’s UID. A mutation can include a blank node as an identifier for the subject or object, or a known UID from a previous mutation.

This is a companion discussion topic for the original entry at https://dgraph.io/docs/mutations/triples/
2

Is it possible to refer to field of another node by uid when using triples?

For example:
_:node1 <Person.father_name> {refer to another Person by uid and return their father.name}

I don’t want to directly refer to another node because I’d like this referred data not to be affected if the referred object is deleted later.

3

You can use an upsert mutation (docs) to do this with a query variable and val().

upsert {
  query {
    var(func: uid(0x123)) {
      fn as father.name
    }
  }
  mutation {
    set {
      <_:node1> <Person.father_name> val(fn) .
    }
  }
}
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