Tips and Tricks with DQL

Get Sample Data

Use the has function to get some sample nodes.

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

curl localhost:8080/query -XPOST -d '
blahblah' | python -m json.tool | less

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
    
	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
    
	"google.golang.org/grpc"
)

var (
	dgraph = flag.String("d", "127.0.0.1:9080", "Dgraph Alpha address")
)

func main() {
	flag.Parse()
	conn, err := grpc.Dial(*dgraph, grpc.WithInsecure())
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	dg := dgo.NewDgraphClient(api.NewDgraphClient(conn))
    
	resp, err := dg.NewTxn().Query(context.Background(), `blahblah`)
	
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Response: %s\n", resp.Json)
}

import io.dgraph.DgraphClient;
import io.dgraph.DgraphGrpc;
import io.dgraph.DgraphGrpc.DgraphStub;
import io.dgraph.DgraphProto.Response;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;

import java.util.Map;

public class App {

    public static void main(final String[] args) {
        ManagedChannel channel =
            ManagedChannelBuilder.forAddress("localhost", 9080).usePlaintext(true).build();
        DgraphStub stub = DgraphGrpc.newStub(channel);
        DgraphClient dgraphClient = new DgraphClient(stub);

        String query = "blahblah";

    
        Response res = dgraphClient.newTransaction().query(query);
    
        System.out.printf("Response: %s", res.getJson().toStringUtf8());
    }
}

import pydgraph
import json

def main():
    client_stub = pydgraph.DgraphClientStub("localhost:9080")
    client = pydgraph.DgraphClient(client_stub)
    query = """blahblah"""
    res = client.txn(read_only=True).query(query)
    print('Response: {}'.format(json.loads(res.json)))

    client_stub.close()


if __name__ == '__main__':
    try:
        main()
    except Exception as e:
        print('Error: {}'.format(e))

const dgraph = require("dgraph-js");
const grpc = require("grpc");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("localhost:9080", grpc.credentials.createInsecure());
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.getJson()));

  clientStub.close();
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

const dgraph = require("dgraph-js-http");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("http://localhost:8080");
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.data));
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

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)
  }
}

curl localhost:8080/query -XPOST -d '
blahblah' | python -m json.tool | less

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
    
	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
    
	"google.golang.org/grpc"
)

var (
	dgraph = flag.String("d", "127.0.0.1:9080", "Dgraph Alpha address")
)

func main() {
	flag.Parse()
	conn, err := grpc.Dial(*dgraph, grpc.WithInsecure())
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	dg := dgo.NewDgraphClient(api.NewDgraphClient(conn))
    
	resp, err := dg.NewTxn().Query(context.Background(), `blahblah`)
	
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Response: %s\n", resp.Json)
}

import io.dgraph.DgraphClient;
import io.dgraph.DgraphGrpc;
import io.dgraph.DgraphGrpc.DgraphStub;
import io.dgraph.DgraphProto.Response;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;

import java.util.Map;

public class App {

    public static void main(final String[] args) {
        ManagedChannel channel =
            ManagedChannelBuilder.forAddress("localhost", 9080).usePlaintext(true).build();
        DgraphStub stub = DgraphGrpc.newStub(channel);
        DgraphClient dgraphClient = new DgraphClient(stub);

        String query = "blahblah";

    
        Response res = dgraphClient.newTransaction().query(query);
    
        System.out.printf("Response: %s", res.getJson().toStringUtf8());
    }
}

import pydgraph
import json

def main():
    client_stub = pydgraph.DgraphClientStub("localhost:9080")
    client = pydgraph.DgraphClient(client_stub)
    query = """blahblah"""
    res = client.txn(read_only=True).query(query)
    print('Response: {}'.format(json.loads(res.json)))

    client_stub.close()


if __name__ == '__main__':
    try:
        main()
    except Exception as e:
        print('Error: {}'.format(e))

const dgraph = require("dgraph-js");
const grpc = require("grpc");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("localhost:9080", grpc.credentials.createInsecure());
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.getJson()));

  clientStub.close();
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

const dgraph = require("dgraph-js-http");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("http://localhost:8080");
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.data));
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

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) }
  }
}

curl localhost:8080/query -XPOST -d '
blahblah' | python -m json.tool | less

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
    
	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
    
	"google.golang.org/grpc"
)

var (
	dgraph = flag.String("d", "127.0.0.1:9080", "Dgraph Alpha address")
)

func main() {
	flag.Parse()
	conn, err := grpc.Dial(*dgraph, grpc.WithInsecure())
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	dg := dgo.NewDgraphClient(api.NewDgraphClient(conn))
    
	resp, err := dg.NewTxn().Query(context.Background(), `blahblah`)
	
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Response: %s\n", resp.Json)
}

import io.dgraph.DgraphClient;
import io.dgraph.DgraphGrpc;
import io.dgraph.DgraphGrpc.DgraphStub;
import io.dgraph.DgraphProto.Response;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;

import java.util.Map;

public class App {

    public static void main(final String[] args) {
        ManagedChannel channel =
            ManagedChannelBuilder.forAddress("localhost", 9080).usePlaintext(true).build();
        DgraphStub stub = DgraphGrpc.newStub(channel);
        DgraphClient dgraphClient = new DgraphClient(stub);

        String query = "blahblah";

    
        Response res = dgraphClient.newTransaction().query(query);
    
        System.out.printf("Response: %s", res.getJson().toStringUtf8());
    }
}

import pydgraph
import json

def main():
    client_stub = pydgraph.DgraphClientStub("localhost:9080")
    client = pydgraph.DgraphClient(client_stub)
    query = """blahblah"""
    res = client.txn(read_only=True).query(query)
    print('Response: {}'.format(json.loads(res.json)))

    client_stub.close()


if __name__ == '__main__':
    try:
        main()
    except Exception as e:
        print('Error: {}'.format(e))

const dgraph = require("dgraph-js");
const grpc = require("grpc");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("localhost:9080", grpc.credentials.createInsecure());
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.getJson()));

  clientStub.close();
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

const dgraph = require("dgraph-js-http");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("http://localhost:8080");
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.data));
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

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 is not 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 is a uid-to-value map mapping
        # starring edges to performance.actor names
        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
        }
      }
    }
  }
}

curl localhost:8080/query -XPOST -d '
blahblah' | python -m json.tool | less

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
    
	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
    
	"google.golang.org/grpc"
)

var (
	dgraph = flag.String("d", "127.0.0.1:9080", "Dgraph Alpha address")
)

func main() {
	flag.Parse()
	conn, err := grpc.Dial(*dgraph, grpc.WithInsecure())
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	dg := dgo.NewDgraphClient(api.NewDgraphClient(conn))
    
	resp, err := dg.NewTxn().Query(context.Background(), `blahblah`)
	
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Response: %s\n", resp.Json)
}

import io.dgraph.DgraphClient;
import io.dgraph.DgraphGrpc;
import io.dgraph.DgraphGrpc.DgraphStub;
import io.dgraph.DgraphProto.Response;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;

import java.util.Map;

public class App {

    public static void main(final String[] args) {
        ManagedChannel channel =
            ManagedChannelBuilder.forAddress("localhost", 9080).usePlaintext(true).build();
        DgraphStub stub = DgraphGrpc.newStub(channel);
        DgraphClient dgraphClient = new DgraphClient(stub);

        String query = "blahblah";

    
        Response res = dgraphClient.newTransaction().query(query);
    
        System.out.printf("Response: %s", res.getJson().toStringUtf8());
    }
}

import pydgraph
import json

def main():
    client_stub = pydgraph.DgraphClientStub("localhost:9080")
    client = pydgraph.DgraphClient(client_stub)
    query = """blahblah"""
    res = client.txn(read_only=True).query(query)
    print('Response: {}'.format(json.loads(res.json)))

    client_stub.close()


if __name__ == '__main__':
    try:
        main()
    except Exception as e:
        print('Error: {}'.format(e))

const dgraph = require("dgraph-js");
const grpc = require("grpc");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("localhost:9080", grpc.credentials.createInsecure());
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.getJson()));

  clientStub.close();
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

const dgraph = require("dgraph-js-http");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("http://localhost:8080");
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.data));
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

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@.
  }
}

curl localhost:8080/query -XPOST -d '
blahblah' | python -m json.tool | less

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
    
	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
    
	"google.golang.org/grpc"
)

var (
	dgraph = flag.String("d", "127.0.0.1:9080", "Dgraph Alpha address")
)

func main() {
	flag.Parse()
	conn, err := grpc.Dial(*dgraph, grpc.WithInsecure())
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	dg := dgo.NewDgraphClient(api.NewDgraphClient(conn))
    
	resp, err := dg.NewTxn().Query(context.Background(), `blahblah`)
	
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Response: %s\n", resp.Json)
}

import io.dgraph.DgraphClient;
import io.dgraph.DgraphGrpc;
import io.dgraph.DgraphGrpc.DgraphStub;
import io.dgraph.DgraphProto.Response;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;

import java.util.Map;

public class App {

    public static void main(final String[] args) {
        ManagedChannel channel =
            ManagedChannelBuilder.forAddress("localhost", 9080).usePlaintext(true).build();
        DgraphStub stub = DgraphGrpc.newStub(channel);
        DgraphClient dgraphClient = new DgraphClient(stub);

        String query = "blahblah";

    
        Response res = dgraphClient.newTransaction().query(query);
    
        System.out.printf("Response: %s", res.getJson().toStringUtf8());
    }
}

import pydgraph
import json

def main():
    client_stub = pydgraph.DgraphClientStub("localhost:9080")
    client = pydgraph.DgraphClient(client_stub)
    query = """blahblah"""
    res = client.txn(read_only=True).query(query)
    print('Response: {}'.format(json.loads(res.json)))

    client_stub.close()


if __name__ == '__main__':
    try:
        main()
    except Exception as e:
        print('Error: {}'.format(e))

const dgraph = require("dgraph-js");
const grpc = require("grpc");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("localhost:9080", grpc.credentials.createInsecure());
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.getJson()));

  clientStub.close();
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

const dgraph = require("dgraph-js-http");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("http://localhost:8080");
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.data));
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

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
  }
}

curl localhost:8080/query -XPOST -d '
blahblah' | python -m json.tool | less

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
    
	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
    
	"google.golang.org/grpc"
)

var (
	dgraph = flag.String("d", "127.0.0.1:9080", "Dgraph Alpha address")
)

func main() {
	flag.Parse()
	conn, err := grpc.Dial(*dgraph, grpc.WithInsecure())
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	dg := dgo.NewDgraphClient(api.NewDgraphClient(conn))
    
	resp, err := dg.NewTxn().Query(context.Background(), `blahblah`)
	
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Response: %s\n", resp.Json)
}

import io.dgraph.DgraphClient;
import io.dgraph.DgraphGrpc;
import io.dgraph.DgraphGrpc.DgraphStub;
import io.dgraph.DgraphProto.Response;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;

import java.util.Map;

public class App {

    public static void main(final String[] args) {
        ManagedChannel channel =
            ManagedChannelBuilder.forAddress("localhost", 9080).usePlaintext(true).build();
        DgraphStub stub = DgraphGrpc.newStub(channel);
        DgraphClient dgraphClient = new DgraphClient(stub);

        String query = "blahblah";

    
        Response res = dgraphClient.newTransaction().query(query);
    
        System.out.printf("Response: %s", res.getJson().toStringUtf8());
    }
}

import pydgraph
import json

def main():
    client_stub = pydgraph.DgraphClientStub("localhost:9080")
    client = pydgraph.DgraphClient(client_stub)
    query = """blahblah"""
    res = client.txn(read_only=True).query(query)
    print('Response: {}'.format(json.loads(res.json)))

    client_stub.close()


if __name__ == '__main__':
    try:
        main()
    except Exception as e:
        print('Error: {}'.format(e))

const dgraph = require("dgraph-js");
const grpc = require("grpc");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("localhost:9080", grpc.credentials.createInsecure());
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.getJson()));

  clientStub.close();
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});

const dgraph = require("dgraph-js-http");

async function main() {
  const clientStub = new dgraph.DgraphClientStub("http://localhost:8080");
  const dgraphClient = new dgraph.DgraphClient(clientStub);

  const query = `blahblah`;
  const response = await dgraphClient.newTxn().query(query);
  console.log("Response: ", JSON.stringify(response.data));
}

main().then().catch((e) => {
  console.log("ERROR: ", e);
});