Tips and Tricks

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Get sample data

Use the has function to get some sample nodes.

{
  result(func: has(director.film), first: 10) {
    uid
    expand(_all_)
  }
}

Count number of connecting nodes

Use expand(_all_) to expand the nodes’ edges, then assign them to a variable. The variable can now be used to iterate over the unique neighboring nodes. Then use count(uid) to count the number of nodes in a block.

{
  uids(func: has(director.film), first: 1) {
    uid
    expand(_all_) {
      u as uid
    }
  }

  result(func: uid(u)) {
    count(uid)
  }
}

Search on non-indexed predicates

Use the has function among the value variables to search on non-indexed predicates.

{
  var(func: has(festival.date_founded)) {
    p as festival.date_founded
  }

  query(func: eq(val(p), "1961-01-01T00:00:00Z")) {
    uid
    name@en
    name@ru
    name@pl
    festival.date_founded
    festival.focus {
      name@en
    }
    festival.individual_festivals {
      total : count(uid)
    }
  }
}

Sort edge by nested node values

Dgraph sorting is based on a single level of the subgraph. To sort a level by the values of a deeper level, use query variables to bring nested values up to the level of the edge to be sorted.

Example: get all actors from a Steven Spielberg movie sorted alphabetically. The actor’s name isn’t accessed from a single traversal from the starring edge. The name is accessible via performance.actor.

{
  spielbergMovies as var(func: allofterms(name@en, "steven spielberg")) {
    name@en
    director.film (orderasc: name@en, first: 1) {
      starring {
        performance.actor {
          ActorName as name@en
        }
      }
      Stars as min(val(ActorName))
    }
  }

  movies(func: uid(spielbergMovies)) @cascade {
    name@en
    director.film (orderasc: name@en, first: 1) {
      name@en
      starring (orderasc: val(Stars)) {
        performance.actor {
          name@en
        }
      }
    }
  }
}

Obtain unique results by using variables

To obtain unique results, assign the node’s edge to a variable. The variable can now be used to iterate over the unique nodes.

Example: get all unique genres from all of the movies directed by Steven Spielberg.

{
  var(func: eq(name@en, "Steven Spielberg")) {
    director.film {
      genres as genre
    }
  }

  q(func: uid(genres)) {
    name@.
  }
}

Usage of checkpwd boolean

Store the result of checkpwd in a query variable and then match it against 1 (checkpwd is true) or 0 (checkpwd is false).

{
  exampleData(func: has(email)) {
    uid
    email
    check as checkpwd(pass, "1bdfhJHb!fd")
  }

  userMatched(func: eq(val(check), 1)) {
    uid
    email
  }

  userIncorrect(func: eq(val(check), 0)) {
    uid
    email
  }
}