Help with recursion

Users Dgraph
1

What I want to do

Perform a recursive query with a second level structure

What I did

Here’s the query I have:

{
      query(func: uid($a)) {
        uid
        created
        leaf (first: 1) {
          stem
        }
        tree {
          uid
          created
          grape (first: 1) {
            num
          }
          branches {  # multiple
            uid
            created
            leaf (first: 1) {
               stem
            }
            tree {
               uid
               created
               grape (first: 1) {
                   num
               }
               branches etc.
            }
          }
        }
      }
    }

I want to replace “branches” with some form of a recursive query such that instead of referring to branches, I could instead point to a function. How would I go about doing that. I tried using the recurse keyword, but that doesn’t seem to like the multi-depth structure of this query. Also pagination asks for a sorting method, but given this sort of query, how would I paginate based on depth? The uid in the filter is what I call the “root node” where all nodes are linked to that specific node. Would I need to create a depth attribute?

2

Not sure if I get it. Something like this?

{
      Root(func: uid($a)) {
        uid
        created
        leaf (first: 1) {
          stem
        }
        tree {
          uid
          created
          grape (first: 1) {
            num
          }
          BRC as branches
        }
      }


   rq(func: uid(BRC)) @recurse {
        uid
        created
        leaf (first: 1)
        stem
        tree
        grape (first: 1)
        num
      }
   }
3

Thanks for the response; the recurse function doesn’t work as expected. rq returns a list that is out of order.

The structure is extremely recursive and follows like this:

{
  query(func: uid($a)) {
    uid
    created
    leaf (first: 1) {
      stem
    }
    tree {
      uid
      created
      grape (first: 1) {
        num
      }
      branches {
        uid
        created
        leaf (first: 1) {
          stem
        }
        tree {
          uid
          created
          grape (first: 1) {
            num
          }
          branches {
            uid
            created
            leaf (first: 1) {
              stem
            }
            tree {
              uid
              created
              grape (first: 1) {
                num
              }
              branches {
                uid
                created
                leaf (first: 1) {
                  stem
                }
                tree {
                  uid
                  created
                  grape (first: 1) {
                    num
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

Right now, rq is returning things out of order, as in sometimes the child branch or tree may be incorrect, and some “tree” are missing.

4

You can try add sorting https://dgraph.io/docs/query-language/sorting/ but the problem is that Recurse isn’t a predictable query.

 rq(func: uid(BRC), orderasc: created) @recurse {
        uid
        created
        leaf (first: 1, orderasc: created)
        stem
        tree
        grape (first: 1, orderasc: created)
        num
      }
5

I didn’t really mean “out of order” in terms of sorting with a created field. I meant that there are missing nodes and sometimes the returned branch and tree edges (in rq) are not real edges.

6

If there are missing nodes, add more edges in order to the recurse expand them. I havent added cuz I dont know your context. But with this example you can go from there.

1 Like
8

The last thing to add in the rq is “branches” otherwise I wouldn’t have gotten full recursion. Thanks!