Cascade Directive
With the @cascade directive, nodes that don’t have all predicates specified in the query are removed. This can be useful in cases where some filter was applied or if nodes might not have all listed predicates.
Query Example: Harry Potter movies, with each actor and characters played. With @cascade, any character not played by an actor called Warwick is removed, as is any Harry Potter movie without any actors called Warwick. Without @cascade, every character is returned, but only those played by actors called Warwick also have the actor name.
{
HP(func: allofterms(name@en, "Harry Potter")) @cascade {
name@en
starring{
performance.character {
name@en
}
performance.actor @filter(allofterms(name@en, "Warwick")){
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);
});
You can apply @cascade on inner query blocks as well.
{
HP(func: allofterms(name@en, "Harry Potter")) {
name@en
genre {
name@en
}
starring @cascade {
performance.character {
name@en
}
performance.actor @filter(allofterms(name@en, "Warwick")){
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);
});