dgo

package module

v1.0.0-...-f8969c1 Latest Latest Go to latest Published: Mar 4, 2019 License: Apache-2.0 Imports: 8 Imported by: 0

Details

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The Go module system was introduced in Go 1.11 and is the official dependency management solution for Go.
Redistributable license

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Tagged version

Modules with tagged versions give importers more predictable builds.
Stable version

When a project reaches major version v1 it is considered stable.
Learn more about best practices

Repository

github.com/ybkimm/dgo

Links

Open Source Insights

README ¶

dgo

Official Dgraph Go client which communicates with the server using gRPC.

Before using this client, we highly recommend that you go through tour.dgraph.io and docs.dgraph.io to understand how to run and work with Dgraph.

Install

go get -u -v github.com/dgraph-io/dgo

Using a client

Create a client

dgraphClient object can be initialised by passing it a list of api.DgraphClient clients as variadic arguments. Connecting to multiple Dgraph servers in the same cluster allows for better distribution of workload.

The following code snippet shows just one connection.

conn, err := grpc.Dial("localhost:9080", grpc.WithInsecure())
if err != nil {
  log.Fatal(err)
}
defer conn.Close()
dgraphClient := dgo.NewDgraphClient(api.NewDgraphClient(conn))

Alter the database

To set the schema, create an instance of api.Operation and use the Alter endpoint.

op := &api.Operation{
  Schema: `name: string @index(exact) .`,
}
err := dgraphClient.Alter(ctx, op)
// Check error

Operation contains other fields as well, including DropAttr and DropAll. DropAll is useful if you wish to discard all the data, and start from a clean slate, without bringing the instance down. DropAttr is used to drop all the data related to a predicate.

Create a transaction

To create a transaction, call dgraphClient.NewTxn(), which returns a *dgo.Txn object. This operation incurs no network overhead.

It is a good practice to call txn.Discard() using a defer statement after it is initialized. Calling txn.Discard() after txn.Commit() is a no-op and you can call txn.Discard() multiple times with no additional side-effects.

txn := dgraphClient.NewTxn()
defer txn.Discard(ctx)

Run a mutation

txn.Mutate(ctx, mu) runs a mutation. It takes in a context.Context and a *api.Mutation object. You can set the data using JSON or RDF N-Quad format.

We define a Person struct to represent a Person and marshal an instance of it to use with Mutation object.

type Person struct {
  Uid  string `json:"uid,omitempty"`
  Name string `json:"name,omitempty"`
}

p := Person{
  Uid:  "_:alice",
  Name: "Alice",
}

pb, err := json.Marshal(p)
if err != nil {
  log.Fatal(err)
}

mu := &api.Mutation{
  SetJson: pb,
}
assigned, err := txn.Mutate(ctx, mu)
if err != nil {
  log.Fatal(err)
}

For a more complete example, see GoDoc.

Sometimes, you only want to commit a mutation, without querying anything further. In such cases, you can use mu.CommitNow = true to indicate that the mutation must be immediately committed.

Run a query

You can run a query by calling txn.Query(ctx, q). You will need to pass in a GraphQL+- query string. If you want to pass an additional map of any variables that you might want to set in the query, call txn.QueryWithVars(ctx, q, vars) with the variables map as third argument.

Let's run the following query with a variable $a:

q := `query all($a: string) {
    all(func: eq(name, $a)) {
      name
    }
  }`

resp, err := txn.QueryWithVars(ctx, q, map[string]string{"$a": "Alice"})
fmt.Println(string(resp.Json))

When running a schema query, the schema response is found in the Schema field of api.Response.

q := `schema(pred: [name]) {
  type
  index
  reverse
  tokenizer
  list
  count
  upsert
  lang
}`

resp, err := txn.Query(ctx, q)
fmt.Println(resp.Schema)

Commit a transaction

A transaction can be committed using the txn.Commit(ctx) method. If your transaction consisted solely of calls to txn.Query or txn.QueryWithVars, and no calls to txn.Mutate, then calling txn.Commit is not necessary.

An error will be returned if other transactions running concurrently modify the same data that was modified in this transaction. It is up to the user to retry transactions when they fail.

txn := dgraphClient.NewTxn()
// Perform some queries and mutations.

err := txn.Commit(ctx)
if err == y.ErrAborted {
  // Retry or handle error
}

Setting Metadata Headers

Metadata headers such as authentication tokens can be set through the context of gRPC methods. Below is an example of how to set a header named "auth-token".

// The following piece of code shows how one can set metadata with
// auth-token, to allow Alter operation, if the server requires it.
md := metadata.New(nil)
md.Append("auth-token", "the-auth-token-value")
ctx := metadata.NewOutgoingContext(context.Background(), md)
dg.Alter(ctx, &op)

Development

Running tests

Make sure you have dgraph installed before you run the tests. This script will run the unit and integration tests.

go test -v ./...

Documentation ¶

Overview ¶

Package dgo is used to interact with a Dgraph server. Queries, mutations, and most other types of admin tasks can be run from the client.

Example (SetObject) ¶

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"time"

	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
	"google.golang.org/grpc"
)

type School struct {
	Name string `json:"name,omitempty"`
}

type loc struct {
	Type   string    `json:"type,omitempty"`
	Coords []float64 `json:"coordinates,omitempty"`
}

// If omitempty is not set, then edges with empty values (0 for int/float, "" for string, false
// for bool) would be created for values not specified explicitly.

type Person struct {
	Uid      string     `json:"uid,omitempty"`
	Name     string     `json:"name,omitempty"`
	Age      int        `json:"age,omitempty"`
	Dob      *time.Time `json:"dob,omitempty"`
	Married  bool       `json:"married,omitempty"`
	Raw      []byte     `json:"raw_bytes,omitempty"`
	Friends  []Person   `json:"friend,omitempty"`
	Location loc        `json:"loc,omitempty"`
	School   []School   `json:"school,omitempty"`
}

func main() {
	conn, err := grpc.Dial("127.0.0.1:9180", grpc.WithInsecure())
	if err != nil {
		log.Fatal("While trying to dial gRPC")
	}
	defer conn.Close()

	dc := api.NewDgraphClient(conn)
	dg := dgo.NewDgraphClient(dc)

	dob := time.Date(1980, 01, 01, 23, 0, 0, 0, time.UTC)
	// While setting an object if a struct has a Uid then its properties in the graph are updated
	// else a new node is created.
	// In the example below new nodes for Alice, Bob and Charlie and school are created (since they
	// dont have a Uid).
	p := Person{
		Name:    "Alice",
		Age:     26,
		Married: true,
		Location: loc{
			Type:   "Point",
			Coords: []float64{1.1, 2},
		},
		Dob: &dob,
		Raw: []byte("raw_bytes"),
		Friends: []Person{{
			Name: "Bob",
			Age:  24,
		}, {
			Name: "Charlie",
			Age:  29,
		}},
		School: []School{{
			Name: "Crown Public School",
		}},
	}

	op := &api.Operation{}
	op.Schema = `
		name: string @index(exact) .
		age: int .
		married: bool .
		loc: geo .
		dob: datetime .
	`

	ctx := context.Background()
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	mu := &api.Mutation{
		CommitNow: true,
	}
	pb, err := json.Marshal(p)
	if err != nil {
		log.Fatal(err)
	}

	mu.SetJson = pb
	assigned, err := dg.NewTxn().Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	// Assigned uids for nodes which were created would be returned in the assigned.Uids map.
	variables := map[string]string{"$id": assigned.Uids["blank-0"]}
	q := `query Me($id: string){
		me(func: uid($id)) {
			name
			dob
			age
			loc
			raw_bytes
			married
			friend @filter(eq(name, "Bob")){
				name
				age
			}
			school {
				name
			}
		}
	}`

	resp, err := dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	type Root struct {
		Me []Person `json:"me"`
	}

	var r Root
	err = json.Unmarshal(resp.Json, &r)
	if err != nil {
		log.Fatal(err)
	}
	// fmt.Printf("Me: %+v\n", r.Me)
	// R.Me would be same as the person that we set above.

	fmt.Println(string(resp.Json))
}

Output:

{"me":[{"name":"Alice","dob":"1980-01-01T23:00:00Z","age":26,"loc":{"type":"Point","coordinates":[1.1,2]},"raw_bytes":"cmF3X2J5dGVz","married":true,"friend":[{"name":"Bob","age":24}],"school":[{"name":"Crown Public School"}]}]}

Index ¶

Variables
func DeleteEdges(mu *api.Mutation, uid string, predicates ...string)
type Dgraph
- func NewDgraphClient(clients ...api.DgraphClient) *Dgraph
type Txn

Constants ¶

This section is empty.

Variables ¶

View Source

var (
	ErrFinished = errors.New("Transaction has already been committed or discarded")
	ErrReadOnly = errors.New("Readonly transaction cannot run mutations or be committed")
)

Functions ¶

func DeleteEdges ¶

func DeleteEdges(mu *api.Mutation, uid string, predicates ...string)

DeleteEdges sets the edges corresponding to predicates on the node with the given uid for deletion. This helper function doesn't run the mutation on the server. It must be done by the user after the function returns.

Example ¶

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"

	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
	"google.golang.org/grpc"
)

func main() {
	conn, err := grpc.Dial("127.0.0.1:9180", grpc.WithInsecure())
	if err != nil {
		log.Fatal("While trying to dial gRPC")
	}
	defer conn.Close()

	dc := api.NewDgraphClient(conn)
	dg := dgo.NewDgraphClient(dc)

	op := &api.Operation{}
	op.Schema = `
			age: int .
			married: bool .
			name: string @lang .
			location: string .
		`

	ctx := context.Background()
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	type School struct {
		Uid  string `json:"uid"`
		Name string `json:"name@en,omitempty"`
	}

	type Person struct {
		Uid      string    `json:"uid,omitempty"`
		Name     string    `json:"name,omitempty"`
		Age      int       `json:"age,omitempty"`
		Married  bool      `json:"married,omitempty"`
		Friends  []Person  `json:"friends,omitempty"`
		Location string    `json:"location,omitempty"`
		Schools  []*School `json:"schools,omitempty"`
	}

	// Lets add some data first.
	p := Person{
		Name:     "Alice",
		Age:      26,
		Married:  true,
		Location: "Riley Street",
		Friends: []Person{{
			Name: "Bob",
			Age:  24,
		}, {
			Name: "Charlie",
			Age:  29,
		}},
		Schools: []*School{&School{
			Name: "Crown Public School",
		}},
	}

	mu := &api.Mutation{}
	pb, err := json.Marshal(p)
	if err != nil {
		log.Fatal(err)
	}

	mu.SetJson = pb
	mu.CommitNow = true
	mu.IgnoreIndexConflict = true
	assigned, err := dg.NewTxn().Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	alice := assigned.Uids["blank-0"]

	variables := make(map[string]string)
	variables["$alice"] = alice
	const q = `query Me($alice: string){
		me(func: uid($alice)) {
			name
			age
			loc
			married
			friends {
				name
				age
			}
			schools {
				name@en
			}
		}
	}`

	resp, err := dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	// Now lets delete the friend and location edge from Alice
	mu = &api.Mutation{}
	dgo.DeleteEdges(mu, alice, "friends", "loc")

	mu.CommitNow = true
	_, err = dg.NewTxn().Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	resp, err = dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	type Root struct {
		Me []Person `json:"me"`
	}

	var r Root
	err = json.Unmarshal(resp.Json, &r)
	fmt.Println(string(resp.Json))
}

Output:

{"me":[{"name":"Alice","age":26,"married":true,"schools":[{"name@en":"Crown Public School"}]}]}

Types ¶

type Dgraph ¶

type Dgraph struct {
	// contains filtered or unexported fields
}

Dgraph is a transaction aware client to a set of dgraph server instances.

func NewDgraphClient ¶

func NewDgraphClient(clients ...api.DgraphClient) *Dgraph

NewDgraphClient creates a new Dgraph for interacting with the Dgraph store connected to in conns. The client can be backed by multiple connections (to the same server, or multiple servers in a cluster).

A single client is thread safe for sharing with multiple go routines.

func (*Dgraph) Alter ¶

func (d *Dgraph) Alter(ctx context.Context, op *api.Operation) error

By setting various fields of api.Operation, Alter can be used to do the following:

1. Modify the schema.

2. Drop a predicate.

3. Drop the database.

Example (DropAll) ¶

package main

import (
	"context"
	"fmt"
	"log"

	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
	"google.golang.org/grpc"
)

func main() {
	conn, err := grpc.Dial("127.0.0.1:9180", grpc.WithInsecure())
	if err != nil {
		log.Fatal("While trying to dial gRPC")
	}
	defer conn.Close()

	dc := api.NewDgraphClient(conn)
	dg := dgo.NewDgraphClient(dc)

	op := api.Operation{
		DropAll: true,
	}
	ctx := context.Background()
	if err := dg.Alter(ctx, &op); err != nil {
		log.Fatal(err)
	}

	fmt.Println(err)

}

Output:

<nil>

func (*Dgraph) GetContext ¶

func (d *Dgraph) GetContext(ctx context.Context) context.Context

func (d *Dgraph) Login(ctx context.Context, userid string, password string) error

func (*Dgraph) NewReadOnlyTxn ¶

func (d *Dgraph) NewReadOnlyTxn() *Txn

func (*Dgraph) NewTxn ¶

func (d *Dgraph) NewTxn() *Txn

NewTxn creates a new transaction.

type Txn ¶

type Txn struct {
	// contains filtered or unexported fields
}

Txn is a single atomic transaction.

A transaction lifecycle is as follows:

1. Created using NewTxn.

2. Various Query and Mutate calls made.

3. Commit or Discard used. If any mutations have been made, It's important that at least one of these methods is called to clean up resources. Discard is a no-op if Commit has already been called, so it's safe to defer a call to Discard immediately after NewTxn.

func (*Txn) BestEffort ¶

func (txn *Txn) BestEffort() *Txn

BestEffort enables best effort in read-only queries. Using this flag will ask the Dgraph Alpha to try to get timestamps from memory in a best effort to reduce the number of outbound requests to Zero. This may yield improved latencies in read-bound datasets.

This method will panic if the transaction is not read-only. Returns the transaction itself.

func (*Txn) Commit ¶

func (txn *Txn) Commit(ctx context.Context) error

Commit commits any mutations that have been made in the transaction. Once Commit has been called, the lifespan of the transaction is complete.

Errors could be returned for various reasons. Notably, ErrAborted could be returned if transactions that modify the same data are being run concurrently. It's up to the user to decide if they wish to retry. In this case, the user should create a new transaction.

func (*Txn) Discard ¶

func (txn *Txn) Discard(ctx context.Context) error

Discard cleans up the resources associated with an uncommitted transaction that contains mutations. It is a no-op on transactions that have already been committed or don't contain mutations. Therefore it is safe (and recommended) to call as a deferred function immediately after a new transaction is created.

In some cases, the transaction can't be discarded, e.g. the grpc connection is unavailable. In these cases, the server will eventually do the transaction clean up.

func (*Txn) Mutate ¶

func (txn *Txn) Mutate(ctx context.Context, mu *api.Mutation) (*api.Assigned, error)

Mutate allows data stored on dgraph instances to be modified. The fields in api.Mutation come in pairs, set and delete. Mutations can either be encoded as JSON or as RDFs.

If CommitNow is set, then this call will result in the transaction being committed. In this case, an explicit call to Commit doesn't need to subsequently be made.

If the mutation fails, then the transaction is discarded and all future operations on it will fail.

Example ¶

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"

	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
	"google.golang.org/grpc"
)

func main() {
	type School struct {
		Name string `json:"name,omitempty"`
	}

	type loc struct {
		Type   string    `json:"type,omitempty"`
		Coords []float64 `json:"coordinates,omitempty"`
	}

	// If omitempty is not set, then edges with empty values (0 for int/float, "" for string, false
	// for bool) would be created for values not specified explicitly.

	type Person struct {
		Uid      string   `json:"uid,omitempty"`
		Name     string   `json:"name,omitempty"`
		Age      int      `json:"age,omitempty"`
		Married  bool     `json:"married,omitempty"`
		Raw      []byte   `json:"raw_bytes,omitempty"`
		Friends  []Person `json:"friend,omitempty"`
		Location loc      `json:"loc,omitempty"`
		School   []School `json:"school,omitempty"`
	}

	conn, err := grpc.Dial("127.0.0.1:9180", grpc.WithInsecure())
	if err != nil {
		log.Fatal("While trying to dial gRPC")
	}
	defer conn.Close()

	dc := api.NewDgraphClient(conn)
	dg := dgo.NewDgraphClient(dc)

	// While setting an object if a struct has a Uid then its properties in the graph are updated
	// else a new node is created.
	// In the example below new nodes for Alice, Bob and Charlie and school are created (since they
	// dont have a Uid).
	p := Person{
		Name:    "Alice",
		Age:     26,
		Married: true,
		Location: loc{
			Type:   "Point",
			Coords: []float64{1.1, 2},
		},
		Raw: []byte("raw_bytes"),
		Friends: []Person{{
			Name: "Bob",
			Age:  24,
		}, {
			Name: "Charlie",
			Age:  29,
		}},
		School: []School{{
			Name: "Crown Public School",
		}},
	}

	op := &api.Operation{}
	op.Schema = `
		age: int .
		married: bool .
	`

	ctx := context.Background()
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	mu := &api.Mutation{
		CommitNow: true,
	}
	pb, err := json.Marshal(p)
	if err != nil {
		log.Fatal(err)
	}

	mu.SetJson = pb
	assigned, err := dg.NewTxn().Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	// Assigned uids for nodes which were created would be returned in the assigned.Uids map.
	puid := assigned.Uids["blank-0"]
	const q = `query Me($id: string){
		me(func: uid($id)) {
			name
			age
			loc
			raw_bytes
			married
			friend @filter(eq(name, "Bob")) {
				name
				age
			}
			school {
				name
			}
		}
	}`

	variables := make(map[string]string)
	variables["$id"] = puid
	resp, err := dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	type Root struct {
		Me []Person `json:"me"`
	}

	var r Root
	err = json.Unmarshal(resp.Json, &r)
	if err != nil {
		log.Fatal(err)
	}

	// R.Me would be same as the person that we set above.
	// fmt.Printf("Me: %+v\n", r.Me)

	fmt.Println(string(resp.Json))
}

Output:

{"me":[{"name":"Alice","age":26,"loc":{"type":"Point","coordinates":[1.1,2]},"raw_bytes":"cmF3X2J5dGVz","married":true,"friend":[{"name":"Bob","age":24}],"school":[{"name":"Crown Public School"}]}]}

Example (Bytes) ¶

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"

	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
	"google.golang.org/grpc"
)

func main() {
	conn, err := grpc.Dial("127.0.0.1:9180", grpc.WithInsecure())
	if err != nil {
		log.Fatal("While trying to dial gRPC")
	}
	defer conn.Close()

	dc := api.NewDgraphClient(conn)
	dg := dgo.NewDgraphClient(dc)

	type Person struct {
		Uid   string `json:"uid,omitempty"`
		Name  string `json:"name,omitempty"`
		Bytes []byte `json:"bytes,omitempty"`
	}

	op := &api.Operation{}
	op.Schema = `
		name: string @index(exact) .
	`

	ctx := context.Background()
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	p := Person{
		Name:  "Alice-new",
		Bytes: []byte("raw_bytes"),
	}

	mu := &api.Mutation{
		CommitNow: true,
	}
	pb, err := json.Marshal(p)
	if err != nil {
		log.Fatal(err)
	}

	mu.SetJson = pb
	_, err = dg.NewTxn().Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	q := `{
	q(func: eq(name, "Alice-new")) {
		name
		bytes
	}
}`

	resp, err := dg.NewTxn().Query(ctx, q)
	if err != nil {
		log.Fatal(err)
	}

	type Root struct {
		Me []Person `json:"q"`
	}

	var r Root
	err = json.Unmarshal(resp.Json, &r)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Me: %+v\n", r.Me)

}

Output:

Me: [{Uid: Name:Alice-new Bytes:[114 97 119 95 98 121 116 101 115]}]

Example (DeleteNode) ¶

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"

	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
	"google.golang.org/grpc"
)

func main() {
	conn, err := grpc.Dial("127.0.0.1:9180", grpc.WithInsecure())
	if err != nil {
		log.Fatal("While trying to dial gRPC")
	}
	defer conn.Close()

	dc := api.NewDgraphClient(conn)
	dg := dgo.NewDgraphClient(dc)

	// In this test we check S * * deletion.
	type Person struct {
		Uid     string    `json:"uid,omitempty"`
		Name    string    `json:"name,omitempty"`
		Age     int       `json:"age,omitempty"`
		Married bool      `json:"married,omitempty"`
		Friends []*Person `json:"friend,omitempty"`
	}

	p := Person{
		Name:    "Alice",
		Age:     26,
		Married: true,
		Friends: []*Person{&Person{
			Name: "Bob",
			Age:  24,
		}, &Person{
			Name: "Charlie",
			Age:  29,
		}},
	}

	op := &api.Operation{}
	op.Schema = `
		age: int .
		married: bool .
	`

	ctx := context.Background()
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	mu := &api.Mutation{
		CommitNow: true,
	}
	pb, err := json.Marshal(p)
	if err != nil {
		log.Fatal(err)
	}

	mu.SetJson = pb
	assigned, err := dg.NewTxn().Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	alice := assigned.Uids["blank-0"]
	bob := assigned.Uids["blank-1"]
	charlie := assigned.Uids["blank-2"]

	variables := make(map[string]string)
	variables["$alice"] = alice
	variables["$bob"] = bob
	variables["$charlie"] = charlie
	const q = `query Me($alice: string, $bob: string, $charlie: string){
		me(func: uid($alice)) {
			name
			age
			married
			friend {
				uid
				name
				age
			}
		}

		me2(func: uid($bob)) {
			name
			age
		}

		me3(func: uid($charlie)) {
			name
			age
		}
	}`

	resp, err := dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	type Root struct {
		Me  []Person `json:"me"`
		Me2 []Person `json:"me2"`
		Me3 []Person `json:"me3"`
	}

	var r Root
	err = json.Unmarshal(resp.Json, &r)

	// Now lets try to delete Alice. This won't delete Bob and Charlie but just remove the
	// connection between Alice and them.

	// The JSON for deleting a node should be of the form {"uid": "0x123"}. If you wanted to
	// delete multiple nodes you could supply an array of objects like [{"uid": "0x321"}, {"uid":
	// "0x123"}] to DeleteJson.

	d := map[string]string{"uid": alice}
	pb, err = json.Marshal(d)
	if err != nil {
		log.Fatal(err)
	}

	mu = &api.Mutation{
		CommitNow:  true,
		DeleteJson: pb,
	}

	_, err = dg.NewTxn().Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	resp, err = dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	err = json.Unmarshal(resp.Json, &r)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("Resp after deleting node: %+v\n", string(resp.Json))
}

Output:

Resp after deleting node: {"me":[],"me2":[{"name":"Bob","age":24}],"me3":[{"name":"Charlie","age":29}]}

Example (DeletePredicate) ¶

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"

	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
	"google.golang.org/grpc"
)

func main() {
	conn, err := grpc.Dial("127.0.0.1:9180", grpc.WithInsecure())
	if err != nil {
		log.Fatal("While trying to dial gRPC")
	}
	defer conn.Close()

	dc := api.NewDgraphClient(conn)
	dg := dgo.NewDgraphClient(dc)

	type Person struct {
		Uid     string   `json:"uid,omitempty"`
		Name    string   `json:"name,omitempty"`
		Age     int      `json:"age,omitempty"`
		Married bool     `json:"married,omitempty"`
		Friends []Person `json:"friend,omitempty"`
	}

	p := Person{
		Name:    "Alice",
		Age:     26,
		Married: true,
		Friends: []Person{Person{
			Name: "Bob",
			Age:  24,
		}, Person{
			Name: "Charlie",
			Age:  29,
		}},
	}

	op := &api.Operation{}
	op.Schema = `
		age: int .
		married: bool .
	`

	ctx := context.Background()
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	mu := &api.Mutation{
		CommitNow: true,
	}
	pb, err := json.Marshal(p)
	if err != nil {
		log.Fatal(err)
	}

	mu.SetJson = pb
	assigned, err := dg.NewTxn().Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	alice := assigned.Uids["blank-0"]

	variables := make(map[string]string)
	variables["$id"] = alice
	const q = `query Me($id: string){
		me(func: uid($id)) {
			name
			age
			married
			friend {
				uid
				name
				age
			}
		}
	}`

	resp, err := dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	type Root struct {
		Me []Person `json:"me"`
	}
	var r Root
	err = json.Unmarshal(resp.Json, &r)
	if err != nil {
		log.Fatal(err)
	}

	op = &api.Operation{
		DropAttr: "friend",
	}
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	op.DropAttr = "married"
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	// Also lets run the query again to verify that predicate data was deleted.
	resp, err = dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	r = Root{}
	err = json.Unmarshal(resp.Json, &r)
	if err != nil {
		log.Fatal(err)
	}

	// Alice should have no friends and only two attributes now.
	fmt.Printf("Response after deletion: %+v\n", r)
}

Output:

Response after deletion: {Me:[{Uid: Name:Alice Age:26 Married:false Friends:[]}]}

Example (List) ¶

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"

	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
	"google.golang.org/grpc"
)

func main() {
	conn, err := grpc.Dial("127.0.0.1:9180", grpc.WithInsecure())
	if err != nil {
		log.Fatal("While trying to dial gRPC")
	}
	defer conn.Close()

	dc := api.NewDgraphClient(conn)
	dg := dgo.NewDgraphClient(dc)
	// This example shows example for SetObject for predicates with list type.
	type Person struct {
		Uid         string   `json:"uid"`
		Address     []string `json:"address"`
		PhoneNumber []int64  `json:"phone_number"`
	}

	p := Person{
		Address:     []string{"Redfern", "Riley Street"},
		PhoneNumber: []int64{9876, 123},
	}

	op := &api.Operation{}
	op.Schema = `
		address: [string] .
		phone_number: [int] .
	`
	ctx := context.Background()
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	mu := &api.Mutation{}
	pb, err := json.Marshal(p)
	if err != nil {
		log.Fatal(err)
	}

	mu.SetJson = pb
	mu.CommitNow = true
	assigned, err := dg.NewTxn().Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	variables := map[string]string{"$id": assigned.Uids["blank-0"]}
	const q = `
	query Me($id: string){
		me(func: uid($id)) {
			address
			phone_number
		}
	}
	`

	resp, err := dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	type Root struct {
		Me []Person `json:"me"`
	}

	var r Root
	err = json.Unmarshal(resp.Json, &r)
	if err != nil {
		log.Fatal(err)
	}

	// List items aren't guaranteed to be in the same order.
	fmt.Println(string(resp.Json))
	// {"me":[{"address":["Riley Street","Redfern"],"phone_number":[9876,123]}]}

}

Output:

func (*Txn) Query ¶

func (txn *Txn) Query(ctx context.Context, q string) (*api.Response, error)

Query sends a query to one of the connected dgraph instances. If no mutations need to be made in the same transaction, it's convenient to chain the method, e.g. NewTxn().Query(ctx, "...").

Example (Besteffort) ¶

dg, cancel := getDgraphClient()
defer cancel()

// NOTE: Best effort only works with read-only queries.
txn := dg.NewReadOnlyTxn().BestEffort()
resp, err := txn.Query(context.Background(), `{ q(func: uid(0x1)) { uid } }`)
if err != nil {
	log.Fatal(err)
}

fmt.Println(string(resp.Json))

Output:

{"q":[{"uid":"0x1"}]}

Example (Unmarshal) ¶

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"

	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
	"google.golang.org/grpc"
)

func main() {
	type School struct {
		Name string `json:"name,omitempty"`
	}

	type Person struct {
		Uid     string   `json:"uid,omitempty"`
		Name    string   `json:"name,omitempty"`
		Age     int      `json:"age,omitempty"`
		Married bool     `json:"married,omitempty"`
		Raw     []byte   `json:"raw_bytes,omitempty"`
		Friends []Person `json:"friend,omitempty"`
		School  []School `json:"school,omitempty"`
	}

	conn, err := grpc.Dial("127.0.0.1:9180", grpc.WithInsecure())
	if err != nil {
		log.Fatal("While trying to dial gRPC")
	}
	defer conn.Close()

	dc := api.NewDgraphClient(conn)
	dg := dgo.NewDgraphClient(dc)

	op := &api.Operation{}
	op.Schema = `
		age: int .
		married: bool .
	`

	ctx := context.Background()
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	p := Person{
		Name: "Bob",
		Age:  24,
	}

	txn := dg.NewTxn()
	pb, err := json.Marshal(p)
	if err != nil {
		log.Fatal(err)
	}

	mu := &api.Mutation{
		CommitNow: true,
		SetJson:   pb,
	}
	assigned, err := txn.Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}
	bob := assigned.Uids["blank-0"]

	// While setting an object if a struct has a Uid then its properties in the graph are updated
	// else a new node is created.
	// In the example below new nodes for Alice and Charlie and school are created (since they dont
	// have a Uid).  Alice is also connected via the friend edge to an existing node Bob.
	p = Person{
		Name:    "Alice",
		Age:     26,
		Married: true,
		Raw:     []byte("raw_bytes"),
		Friends: []Person{{
			Uid: bob,
		}, {
			Name: "Charlie",
			Age:  29,
		}},
		School: []School{{
			Name: "Crown Public School",
		}},
	}

	txn = dg.NewTxn()
	mu = &api.Mutation{}
	pb, err = json.Marshal(p)
	if err != nil {
		log.Fatal(err)
	}

	mu.SetJson = pb
	mu.CommitNow = true
	assigned, err = txn.Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	// Assigned uids for nodes which were created would be returned in the assigned.Uids map.
	puid := assigned.Uids["blank-0"]
	variables := make(map[string]string)
	variables["$id"] = puid
	const q = `query Me($id: string){
		me(func: uid($id)) {
			name
			age
			loc
			raw_bytes
			married
			friend @filter(eq(name, "Bob")) {
				name
				age
			}
			school {
				name
			}
		}
	}`

	resp, err := dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	type Root struct {
		Me []Person `json:"me"`
	}

	var r Root
	err = json.Unmarshal(resp.Json, &r)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println(string(resp.Json))
}

Output:

{"me":[{"name":"Alice","age":26,"raw_bytes":"cmF3X2J5dGVz","married":true,"friend":[{"name":"Bob","age":24}],"school":[{"name":"Crown Public School"}]}]}

Example (Variables) ¶

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"

	"github.com/dgraph-io/dgo"
	"github.com/dgraph-io/dgo/protos/api"
	"google.golang.org/grpc"
)

func main() {
	conn, err := grpc.Dial("127.0.0.1:9180", grpc.WithInsecure())
	if err != nil {
		log.Fatal("While trying to dial gRPC")
	}
	defer conn.Close()

	dc := api.NewDgraphClient(conn)
	dg := dgo.NewDgraphClient(dc)

	type Person struct {
		Uid  string `json:"uid,omitempty"`
		Name string `json:"name,omitempty"`
	}

	op := &api.Operation{}
	op.Schema = `
		name: string @index(exact) .
	`

	ctx := context.Background()
	err = dg.Alter(ctx, op)
	if err != nil {
		log.Fatal(err)
	}

	p := Person{
		Name: "Alice",
	}

	mu := &api.Mutation{
		CommitNow: true,
	}
	pb, err := json.Marshal(p)
	if err != nil {
		log.Fatal(err)
	}

	mu.SetJson = pb
	_, err = dg.NewTxn().Mutate(ctx, mu)
	if err != nil {
		log.Fatal(err)
	}

	variables := make(map[string]string)
	variables["$a"] = "Alice"
	q := `query Alice($a: string){
		me(func: eq(name, $a)) {
			name
		}
	}`

	resp, err := dg.NewTxn().QueryWithVars(ctx, q, variables)
	if err != nil {
		log.Fatal(err)
	}

	type Root struct {
		Me []Person `json:"me"`
	}

	var r Root
	err = json.Unmarshal(resp.Json, &r)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println(string(resp.Json))
}

Output:

{"me":[{"name":"Alice"}]}

func (*Txn) QueryWithVars ¶

func (txn *Txn) QueryWithVars(ctx context.Context, q string,
	vars map[string]string) (*api.Response, error)

QueryWithVars is like Query, but allows a variable map to be used. This can provide safety against injection attacks.

func (*Txn) Sequencing ¶

func (txn *Txn) Sequencing(sequencing api.LinRead_Sequencing)

Source Files ¶

View all Source files

Directories ¶

Path	Synopsis
protos
api
x
y Package y contains the code shared by the Go client and Dgraph server.	Package y contains the code shared by the Go client and Dgraph server.

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