图计算Dgraph系列2-Schema操作

       <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>
        </dependency>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.8.5</version>
        </dependency>
        <dependency>
            <groupId>io.dgraph</groupId>
            <artifactId>dgraph4j</artifactId>
            <version>20.03.0</version>
        </dependency>

public static DgraphClient getDgraphClient() {
    ManagedChannel channel =
            ManagedChannelBuilder.forAddress("localhost",9080).usePlaintext().build();

    DgraphGrpc.DgraphStub stub = DgraphGrpc.newStub(channel);

    DgraphClient dgraphClient = new DgraphClient(stub);
    return  dgraphClient;
}

String schema = "name: string @index(exact, term) .\n" +
                "boss_of: [uid] .\n" +
                "works_for: [uid] .\n" +
                "industry: string @index(term) .\n" +
                "work_here: [uid] ."
            ;
        Operation operation = Operation.newBuilder().setSchema(schema).build();
        dgraphClient.alter(operation);

//先删除，再添加，不然报 io.grpc.StatusRuntimeException: UNKNOWN: Type can't be changed from list to scalar for attr: [boss_of] without dropping it first.
dgraphClient.alter(Operation.newBuilder().setDropAttr("boss_of").build());
String schema =
        "boss_of: string .\n"
    ;
Operation operation = Operation.newBuilder().setSchema(schema).build();
dgraphClient.alter(operation);

String schema =
        "type Person {\n" +
            "name\n" +
            "age\n" +
        "}"
    ;
Operation operation = Operation.newBuilder().setSchema(schema).build();
dgraphClient.alter(operation);

// 报异常，因为age没有在Predicates定义

String schema =
                "type Person {\n" +
                    "name\n" +
                    "boss_of\n" +
                "}"
            ;
        Operation operation = Operation.newBuilder().setSchema(schema).build();
        dgraphClient.alter(operation);

final DgraphClient dgraphClient = getDgraphClient();
//删除schema + 数据
dgraphClient.alter(Operation.newBuilder().setDropAll(true).build());

String schema =
        "industry: string @index(term) .\n" +
        "boss_of: [uid] .\n" +
        "name: string @index(exact, term) .\n" +
        "works_for: [uid] .\n" +
        "work_here: [uid] .\n" +

        "type Person {\n" +
        "    name\n" +
        "    boss_of\n" +
        "    works_for\n" +
        "}\n" +
        "type Company {\n" +
        "    name\n" +
        "    industry\n" +
        "    work_here \n" +
        "}"
    ;
Operation operation = Operation.newBuilder().setSchema(schema).build();
dgraphClient.alter(operation);

schema(sch:[name, work_here, age, Person]) {
  type
  index
}

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

func main() {
	client := getClient()
	createSchema(client)
}

func createSchema(client *dgo.Dgraph) error {
	schema := "name: string @index(term) . \n" +
		"age: int .\n" +
		"address: string .\n" +
		"type Person {\n" +
		"\tname\n" +
		"\tage\n" +
		"\taddress\n" +
		"}"

	ctx := context.Background()
	err :=  client.Alter(ctx, &api.Operation{Schema: schema})

	return err
}

func alterSchema(client *dgo.Dgraph) error {
	schema := "address: string @index(fulltext) . \n"
	ctx := context.Background()

	err :=  client.Alter(ctx, &api.Operation{Schema: schema})
	return err
}

func dropSchema(client *dgo.Dgraph) error {
	//err :=  client.Alter(context.Background(), &api.Operation{DropOp: api.Operation_DATA})
	//这种type操作没有成功，怎么删除Person
	//err :=  client.Alter(context.Background(), &api.Operation{DropOp: api.Operation_TYPE})
	//删除数据和schema
	err :=  client.Alter(context.Background(), &api.Operation{DropAll: true})
	return err
}