Adding xid field to graph.Node and passing pointer to destination node in

preTraverse()

query/graph/graphresponse.pb.go

@@ -53,9 +53,10 @@ func (*Value) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{1} }
 
 type Node struct {
 	Uid        uint64            `protobuf:"varint,1,opt,name=uid" json:"uid,omitempty"`
-	Attribute  string            `protobuf:"bytes,2,opt,name=attribute" json:"attribute,omitempty"`
-	Properties map[string]*Value `protobuf:"bytes,3,rep,name=properties" json:"properties,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
-	Children   []*Node           `protobuf:"bytes,4,rep,name=children" json:"children,omitempty"`
+	Xid        string            `protobuf:"bytes,2,opt,name=xid" json:"xid,omitempty"`
+	Attribute  string            `protobuf:"bytes,3,opt,name=attribute" json:"attribute,omitempty"`
+	Properties map[string]*Value `protobuf:"bytes,4,rep,name=properties" json:"properties,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
+	Children   []*Node           `protobuf:"bytes,5,rep,name=children" json:"children,omitempty"`
 }
 
 func (m *Node) Reset()                    { *m = Node{} }
@@ -155,22 +156,22 @@ var _DGraph_serviceDesc = grpc.ServiceDesc{
 }
 
 var fileDescriptor0 = []byte{
-	// 266 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x5c, 0x90, 0x41, 0x4b, 0xc3, 0x40,
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-	0x35, 0x0a, 0x1e, 0x26, 0xe7, 0xb0, 0x2b, 0xe9, 0xab, 0xa3, 0xd6, 0xe0, 0x31, 0x88, 0xbe, 0xd0,
-	0xab, 0xd8, 0x9b, 0x79, 0xf3, 0xb1, 0x5c, 0x37, 0xfd, 0x82, 0x78, 0xcb, 0x97, 0x1d, 0xe1, 0x09,
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-	0x92, 0x83, 0x75, 0xbc, 0x84, 0xbd, 0xf7, 0x85, 0x5a, 0x96, 0x9a, 0xaa, 0x38, 0xe0, 0xd3, 0x68,
-	0x70, 0x2a, 0x37, 0x70, 0xfa, 0x04, 0x07, 0x5b, 0x3a, 0xd6, 0xe8, 0x27, 0xfd, 0xbd, 0x69, 0x4b,
-	0x4c, 0x40, 0x7c, 0xdb, 0x27, 0xd9, 0x64, 0x94, 0x4d, 0x9c, 0x14, 0x3f, 0x2e, 0xd7, 0xe8, 0x76,
-	0x74, 0xe3, 0x65, 0x57, 0x10, 0xde, 0x3f, 0x5a, 0x84, 0x17, 0x20, 0x5e, 0x6d, 0x3e, 0xb8, 0xef,
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-	0xff, 0xff, 0x2c, 0xc9, 0x79, 0xe9, 0x84, 0x01, 0x00, 0x00,
+	// 272 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x5c, 0x50, 0xc1, 0x4a, 0xc3, 0x40,
+	0x10, 0x35, 0x4d, 0x36, 0xda, 0x49, 0x51, 0x19, 0x45, 0x42, 0x15, 0x2c, 0x39, 0x68, 0x4f, 0x41,
+	0xe2, 0x45, 0xf4, 0xaa, 0x78, 0x10, 0x44, 0xf7, 0xe0, 0x3d, 0x31, 0x83, 0x5d, 0x2c, 0x49, 0xdc,
+	0x6c, 0xc4, 0x7e, 0xbb, 0x17, 0xb3, 0xd3, 0xb5, 0x06, 0x6f, 0x6f, 0xdf, 0x9b, 0x79, 0xfb, 0xe6,
+	0xc1, 0xc1, 0x9b, 0xce, 0x9b, 0x85, 0xa6, 0xb6, 0xa9, 0xab, 0x96, 0xd2, 0x46, 0xd7, 0xa6, 0x46,
+	0xc1, 0x64, 0x72, 0x0a, 0xdb, 0x92, 0x3e, 0x3a, 0x6a, 0x0d, 0x1e, 0x82, 0xe8, 0x81, 0x5e, 0xc5,
+	0xde, 0xcc, 0x9b, 0x8f, 0xe5, 0xfa, 0xd1, 0x0f, 0x88, 0x97, 0x7c, 0xd9, 0x11, 0x1e, 0x41, 0x58,
+	0xa8, 0x2a, 0x77, 0xfa, 0x44, 0xba, 0x57, 0xf2, 0xed, 0x41, 0xf0, 0x58, 0x97, 0x84, 0xfb, 0xe0,
+	0x77, 0xaa, 0x64, 0x35, 0x90, 0x16, 0x5a, 0xe6, 0xab, 0x67, 0x46, 0xec, 0x67, 0x21, 0x9e, 0xc0,
+	0x38, 0x37, 0x46, 0xab, 0xa2, 0x33, 0x14, 0xfb, 0xcc, 0xff, 0x11, 0x78, 0x03, 0xd0, 0x87, 0x6b,
+	0x48, 0x1b, 0x45, 0x6d, 0x1c, 0xcc, 0xfc, 0x79, 0x94, 0x1d, 0xa7, 0x1c, 0x34, 0xb5, 0x5f, 0xa4,
+	0x4f, 0x1b, 0xf5, 0xae, 0x32, 0x7a, 0x25, 0x07, 0xe3, 0x78, 0x0e, 0x3b, 0xaf, 0x0b, 0xb5, 0x2c,
+	0x35, 0x55, 0xb1, 0xe0, 0xd5, 0x68, 0xb0, 0x2a, 0x37, 0xe2, 0xf4, 0x01, 0xf6, 0xfe, 0xf9, 0xd8,
+	0xa0, 0xef, 0xf4, 0x7b, 0xb8, 0x85, 0x98, 0x80, 0xf8, 0xb4, 0x67, 0x73, 0xf8, 0x28, 0x9b, 0x38,
+	0x2b, 0xae, 0x42, 0xae, 0xa5, 0xeb, 0xd1, 0x95, 0x97, 0x5d, 0x40, 0x78, 0x7b, 0x6f, 0x25, 0x3c,
+	0x03, 0xf1, 0x6c, 0x1b, 0xc3, 0x5d, 0x37, 0xeb, 0x7a, 0x9d, 0x0e, 0x63, 0x24, 0x5b, 0x45, 0xc8,
+	0xfd, 0x5f, 0xfe, 0x04, 0x00, 0x00, 0xff, 0xff, 0xb8, 0x91, 0x31, 0x0d, 0x96, 0x01, 0x00, 0x00,
 }

query/graph/graphresponse.proto

@@ -18,7 +18,8 @@ message Value {
 
 message Node {
   uint64 uid = 1;
-  string attribute = 2;
-  map<string, Value> properties = 3;
-  repeated Node children = 4; // Each node can have multiple children
+  string xid = 2;
+  string attribute = 3;
+  map<string, Value> properties = 4;
+  repeated Node children = 5; // Each node can have multiple children
 }

query/query.go

@@ -271,18 +271,19 @@ func indexOf(uid uint64, q *task.Query) int {
 }
 
 // This method gets the values and children for a subgraph.
-func preTraverse(uid uint64, g *SubGraph) (map[string]*graph.Value, []*graph.Node, error) {
-	values := make(map[string]*graph.Value)
+func (g *SubGraph) preTraverse(uid uint64, dst *graph.Node) error {
+	properties := make(map[string]*graph.Value)
 	var children []*graph.Node
 
-	for _, predChild := range g.Children {
-		ro := flatbuffers.GetUOffsetT(predChild.result)
+	// We go through all predicate children of the subgraph.
+	for _, pc := range g.Children {
+		ro := flatbuffers.GetUOffsetT(pc.result)
 		r := new(task.Result)
-		r.Init(predChild.result, ro)
+		r.Init(pc.result, ro)
 
-		uo := flatbuffers.GetUOffsetT(predChild.query)
+		uo := flatbuffers.GetUOffsetT(pc.query)
 		q := new(task.Query)
-		q.Init(predChild.query, uo)
+		q.Init(pc.query, uo)
 
 		idx := indexOf(uid, q)
 
@@ -290,15 +291,15 @@ func preTraverse(uid uint64, g *SubGraph) (map[string]*graph.Value, []*graph.Nod
 			glog.WithFields(logrus.Fields{
 				"uid":            uid,
 				"attribute":      g.Attr,
-				"childAttribute": predChild.Attr,
+				"childAttribute": pc.Attr,
 			}).Fatal("Attribute with uid not found in child Query uids")
-			return values, children, fmt.Errorf("Attribute with uid not found")
+			return fmt.Errorf("Attribute with uid not found")
 		}
 
 		var ul task.UidList
 		var tv task.Value
 		if ok := r.Uidmatrix(&ul, idx); !ok {
-			return values, children, fmt.Errorf("While parsing UidList")
+			return fmt.Errorf("While parsing UidList")
 		}
 
 		if ul.UidsLength() > 0 {
@@ -306,28 +307,25 @@ func preTraverse(uid uint64, g *SubGraph) (map[string]*graph.Value, []*graph.Nod
 			// this predicate.
 			for i := 0; i < ul.UidsLength(); i++ {
 				uid := ul.Uids(i)
-				uidChild := new(graph.Node)
-				uidChild.Attribute = predChild.Attr
-				uidChild.Uid = uid
-
-				vals, ch, rerr := preTraverse(uid, predChild)
-				if rerr != nil {
+				uc := new(graph.Node)
+				uc.Attribute = pc.Attr
+				uc.Uid = uid
+				if rerr := pc.preTraverse(uid, uc); rerr != nil {
 					x.Err(glog, rerr).Error("Error while traversal")
-					return values, children, rerr
+					return rerr
 				}
 
-				uidChild.Properties, uidChild.Children = vals, ch
-				children = append(children, uidChild)
+				children = append(children, uc)
 			}
 		} else {
 			v := new(graph.Value)
 			if ok := r.Values(&tv, idx); !ok {
-				return values, children, fmt.Errorf("While parsing value")
+				return fmt.Errorf("While parsing value")
 			}
 
 			var ival interface{}
 			if err := posting.ParseValue(&ival, tv.ValBytes()); err != nil {
-				return values, children, err
+				return err
 			}
 
 			if ival == nil {
@@ -335,10 +333,14 @@ func preTraverse(uid uint64, g *SubGraph) (map[string]*graph.Value, []*graph.Nod
 			}
 
 			v.Binary = []byte(ival.(string))
-			values[predChild.Attr] = v
+			properties[pc.Attr] = v
 		}
 	}
-	return values, children, nil
+	if val, ok := properties["xid"]; ok {
+		dst.Xid = string(val.Binary)
+	}
+	dst.Properties, dst.Children = properties, children
+	return nil
 }
 
 // This method transforms the predicate based subgraph to an
@@ -358,8 +360,7 @@ func (g *SubGraph) ToProtocolBuffer(l *Latency) (n *graph.Node, rerr error) {
 	r.Uidmatrix(&ul, 0)
 	n.Uid = ul.Uids(0)
 
-	n.Properties, n.Children, rerr = preTraverse(n.Uid, g)
-	if rerr != nil {
+	if rerr = g.preTraverse(n.Uid, n); rerr != nil {
 		x.Err(glog, rerr).Error("Error while traversal")
 		return n, rerr
 	}

query/query_test.go

@@ -184,6 +184,9 @@ func populateGraph(t *testing.T) (string, *store.Store) {
 	edge.Value = "Andrea"
 	addEdge(t, edge, posting.GetOrCreate(posting.Key(31, "name"), ps))
 
+	edge.Value = "mich"
+	addEdge(t, edge, posting.GetOrCreate(posting.Key(1, "xid"), ps))
+
 	return dir, ps
 }
 
@@ -327,6 +330,7 @@ func TestToProtocolBuffer(t *testing.T) {
 	query := `
 		{
 			me(_uid_:0x01) {
+				xid
 				name
 				gender
 				status
@@ -367,8 +371,11 @@ func TestToProtocolBuffer(t *testing.T) {
 	if gr.Uid != 1 {
 		t.Errorf("Expected uid 1, Got: %v", gr.Uid)
 	}
-	if len(gr.Properties) != 3 {
-		t.Errorf("Expected values map to contain 3 properties, Got: %v",
+	if gr.Xid != "mich" {
+		t.Errorf("Expected xid mich, Got: %v", gr.Xid)
+	}
+	if len(gr.Properties) != 4 {
+		t.Errorf("Expected values map to contain 4 properties, Got: %v",
 			len(gr.Properties))
 	}
 	if string(gr.Properties["name"].Binary) != "Michonne" {