Query to detect a missing edge

Users Dgraph
1

Hello, I’m trying to write a specific query, and just cannot work out how to achieve this one. Any help appreciated!

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For every Edge1 in my database, this exact pattern should exist. However in some cases Edge3 can be missing, so I’m trying to find all Node3-Node4 pairs where Edge3 is missing (or even better, add the link in directly).

Ideally I need to iterate through all Edge1’s in a single query, as there are many millions of them and I do not want to issue a query for each edge.

This is the best query I managed to come up with:

upsert {
  query {
    A as var(func:has(Node1.Edge1)) {~Node4.Edge4 {B as uid}}
	
	var(func:uid(A)) {
	  Node1.Edge1 {
		~Node3.Edge2 {
          C as uid
          ~Node4.Edge3 @filter(uid(B))
           {D as uid}
		}
	  }
    }
  }

  mutation @if(not eq(len(D), 1)) {
    set {
      uid(B) <Node4.Edge3> uid(C) .
    }
  }
}

However this has the issue that is will cartesian all B’s and C’s together from all results, it is not limited to just this one loop/pattern.

I also tried standard queries to just return the B/C pairs with missing Edge3’s, but all had this cartesian problem whatever I tried.