From e2e340dfc0789227eb67acbd4d4869761760e63f Mon Sep 17 00:00:00 2001
From: srfrog <gus@dgraph.io>
Date: Thu, 28 Mar 2019 15:09:13 -0700
Subject: [PATCH] example_mutation_txn_test.go: example of using conditional
 mutation txn

---
 example_mutation_txn_test.go | 121 +++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 example_mutation_txn_test.go

diff --git a/example_mutation_txn_test.go b/example_mutation_txn_test.go
new file mode 100644
index 0000000..a03eb70
--- /dev/null
+++ b/example_mutation_txn_test.go
@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) 2019 Dgraph Labs, Inc. and Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package dgo_test
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/dgraph-io/dgo"
+	"github.com/dgraph-io/dgo/protos/api"
+	"google.golang.org/grpc"
+)
+
+// ExampleTxn_Mutation__Txn shows a txn mutation with a conditional query.
+// The complete mutation looks like this:
+//
+// txn {
+//   query {
+//     me(func: eq(email, "gus@dgrapho.io")) {
+//       v as uid
+//     }
+//   }
+//   mutation {
+//     set {
+//       uid(v) <email> "gus@dgraph.io" .
+//     }
+//   }
+// }
+func Example_txnMutation() {
+	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 = `
+		name: string .
+		email: string @index(exact) .
+	`
+
+	ctx := context.Background()
+	err = dg.Alter(ctx, op)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	mutation1 := `
+		_:n1 <name> "srfrog" .
+		_:n1 <email> "gus@dgraphO.io" .
+	`
+
+	mu := &api.Mutation{
+		SetNquads: []byte(mutation1),
+		CommitNow: true,
+	}
+
+	// add a node
+	_, err = dg.NewTxn().Mutate(ctx, mu)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// conditional query on v var
+	condQuery := `
+		query {
+			me(func: eq(email, "gus@dgraphO.io")) {
+				v as uid
+			}
+		}
+	`
+	// mutation based on conditional
+	mutation2 := `
+		uid(v) <email> "gus@dgraph.io" .
+	`
+
+	mu.CondQuery = condQuery
+	mu.SetNquads = []byte(mutation2)
+
+	// Update email only if matching uid found.
+	_, err = dg.NewTxn().Mutate(ctx, mu)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	query := `
+	{
+		me(func: eq(email, "gus@dgraph.io")) {
+			name
+			email
+		}
+	}`
+
+	// query to verify the change
+	resp, err := dg.NewTxn().Query(ctx, query)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// resp.Json contains the updated value.
+	fmt.Println(string(resp.Json))
+	// Output: {"me":[{"name":"srfrog","email":"gus@dgraph.io"}]}
+}