Add support to show metrics

query/outputnode.go

@@ -41,15 +41,19 @@ import (
 // ToJson converts the list of subgraph into a JSON response by calling toFastJSON.
 func ToJson(l *Latency, sgl []*SubGraph) ([]byte, error) {
 	sgr := &SubGraph{}
+	metricsMap := map[string]int{}
 	for _, sg := range sgl {
 		if sg.Params.Alias == "var" || sg.Params.Alias == "shortest" {
 			continue
 		}
 		if sg.Params.GetUid {
 			sgr.Params.GetUid = true
 		}
+		// calculate metrics for this query.
+		calculateMetrics(sg, metricsMap)
 		sgr.Children = append(sgr.Children, sg)
 	}
+	fmt.Println(metricsMap)
 	return sgr.toFastJSON(l)
 }
 
@@ -810,3 +814,23 @@ func (sg *SubGraph) preTraverse(uid uint64, dst outputNode) error {
 
 	return nil
 }
+
+// calculateMetrics populates the given map with the number of uids are gathered for each
+// attributes.
+func calculateMetrics(sg *SubGraph, metrics map[string]int) {
+	// we'll calculate srcUid of the each attribute. because, these are number of uids
+	// processed by this attribute.
+	prev := metrics[sg.Attr]
+	// QUESTION: @manish @pawan: should I add destuid or length of posting list?.
+	prev = prev + len(sg.SrcUIDs.GetUids())
+	metrics[sg.Attr] = prev
+
+	// add all the uids gathered by filters
+	for _, filter := range sg.Filters {
+		calculateMetrics(filter, metrics)
+	}
+	// calculate metrics for the childres as well.
+	for _, child := range sg.Children {
+		calculateMetrics(child, metrics)
+	}
+}