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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.
Depending on the version of Dgraph that you are connecting to, you will have to use a different version of this client and their corresponding import paths.
| Dgraph version | dgo version | dgo import path |
|---|---|---|
| dgraph 1.0.X | dgo 1.X.Y | "github.com/dgraph-io/dgo" |
| dgraph 1.1.X | dgo 2.X.Y | "github.com/dgraph-io/dgo/v2" |
Note: One of the most important API breakages from dgo v1 to v2 is in
the function dgo.Txn.Mutate. This function returns an *api.Assigned
value in v1 but an *api.Response in v2.
dgraphClient object can be initialized 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))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 errorOperation 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.
Starting Dgraph version 20.03.0, indexes can be computed in the background.
You can set RunInBackground field of the api.Operation to true
before passing it to the Alter function. You can find more details
here.
op := &api.Operation{
Schema: `name: string @index(exact) .`,
RunInBackground: true
}
err := dgraphClient.Alter(ctx, op)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)Read-only transactions can be created by calling c.NewReadOnlyTxn(). Read-only
transactions are useful to increase read speed because they can circumvent the
usual consensus protocol. Read-only transactions cannot contain mutations and
trying to call txn.Commit() will result in an error. Calling txn.Discard()
will be a no-op.
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.
To use JSON, use the fields SetJson and DeleteJson, which accept a string representing the nodes to be added or removed respectively (either as a JSON map or a list). To use RDF, use the fields SetNquads and DeleteNquads, which accept a string representing the valid RDF triples (one per line) to added or removed respectively. This protobuf object also contains the Set and Del fields which accept a list of RDF triples that have already been parsed into our internal format. As such, these fields are mainly used internally and users should use the SetNquads and DeleteNquads instead if they are planning on using RDF.
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"`
DType []string `json:"dgraph.type,omitempty"`
}
p := Person{
Uid: "_:alice",
Name: "Alice",
DType: []string{"Person"},
}
pb, err := json.Marshal(p)
if err != nil {
log.Fatal(err)
}
mu := &api.Mutation{
SetJson: pb,
}
res, 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.
Mutation can be run using txn.Do as well.
mu := &api.Mutation{
SetJson: pb,
}
req := &api.Request{CommitNow:true, Mutations: []*api.Mutation{mu}}
res, err := txn.Do(ctx, req)
if err != nil {
log.Fatal(err)
}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, $a)) {
name
}
}`
res, err := txn.QueryWithVars(ctx, q, map[string]string{"$a": "Alice"})
fmt.Printf("%s\n", res.Json)You can also use txn.Do function to run a query.
req := &api.Request{
Query: q,
Vars: map[string]string{"$a": "Alice"},
}
res, err := txn.Do(ctx, req)
if err != nil {
log.Fatal(err)
}
fmt.Printf("%s\n", res.Json)When running a schema query for predicate name, the schema response is found
in the Json field of api.Response as shown below:
q := `schema(pred: [name]) {
type
index
reverse
tokenizer
list
count
upsert
lang
}`
res, err := txn.Query(ctx, q)
if err != nil {
log.Fatal(err)
}
fmt.Printf("%s\n", res.Json)The txn.Do function allows you to run upserts consisting of one query and
one mutation. Variables can be defined in the query and used in the mutation.
You could also use txn.Do to perform a query followed by a mutation.
To know more about upsert, we highly recommend going through the docs at https://docs.dgraph.io/mutations/#upsert-block.
query = `
query {
user as var(func: eq(email, "[email protected]"))
}`
mu := &api.Mutation{
SetNquads: []byte(`uid(user) <email> "[email protected]" .`),
}
req := &api.Request{
Query: query,
Mutations: []*api.Mutation{mu},
CommitNow:true,
}
// Update email only if matching uid found.
if _, err := dg.NewTxn().Do(ctx, req); err != nil {
log.Fatal(err)
}The upsert block also allows specifying a conditional mutation block using an @if directive.
The mutation is executed only when the specified condition is true. If the condition is false,
the mutation is silently ignored.
See more about Conditional Upsert Here.
query = `
query {
user as var(func: eq(email, "[email protected]"))
}`
mu := &api.Mutation{
Cond: `@if(eq(len(user), 1))`, // Only mutate if "[email protected]" belongs to single user.
SetNquads: []byte(`uid(user) <email> "[email protected]" .`),
}
req := &api.Request{
Query: query,
Mutations: []*api.Mutation{mu},
CommitNow:true,
}
// Update email only if exactly one matching uid is found.
if _, err := dg.NewTxn().Do(ctx, req); err != nil {
log.Fatal(err)
}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
}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)Make sure you have dgraph installed before you run the tests. This script will run the unit and
integration tests.
go test -v ./...