fix: interpret missing point as zero value in formula evaluation (#4668)

pkg/query-service/app/formula.go

@@ -87,23 +87,6 @@ func joinAndCalculate(results []*v3.Result, uniqueLabelSet map[string]string, ex
 		}
 	}
 
-	vars := expression.Vars()
-	var doesNotHaveAllVars bool
-	for _, v := range vars {
-		if _, ok := seriesMap[v]; !ok {
-			doesNotHaveAllVars = true
-			break
-		}
-	}
-
-	// There is no series that matches the label set from all queries
-	// TODO: Does the lack of a series from one query mean that the result should be nil?
-	// Or should we interpret the series as having a value of 0 at all timestamps?
-	// The current behaviour with ClickHouse is to show no data
-	if doesNotHaveAllVars {
-		return nil, nil
-	}
-
 	resultSeries := &v3.Series{
 		Labels: uniqueLabelSet,
 	}

pkg/query-service/app/formula_test.go

@@ -235,7 +235,39 @@ func TestProcessResults(t *testing.T) {
 				},
 			},
 			want: &v3.Result{
-				Series: []*v3.Series{},
+				Series: []*v3.Series{
+					{
+						Labels: map[string]string{
+							"service_name": "frontend",
+							"operation":    "GET /api",
+						},
+						Points: []v3.Point{
+							{
+								Timestamp: 1,
+								Value:     10,
+							},
+							{
+								Timestamp: 2,
+								Value:     20,
+							},
+						},
+					},
+					{
+						Labels: map[string]string{
+							"service_name": "redis",
+						},
+						Points: []v3.Point{
+							{
+								Timestamp: 1,
+								Value:     30,
+							},
+							{
+								Timestamp: 3,
+								Value:     40,
+							},
+						},
+					},
+				},
 			},
 		},
 	}
@@ -350,6 +382,21 @@ func TestProcessResultsErrorRate(t *testing.T) {
 			},
 			want: &v3.Result{
 				Series: []*v3.Series{
+					{
+						Labels: map[string]string{
+							"service_name": "frontend",
+						},
+						Points: []v3.Point{
+							{
+								Timestamp: 1,
+								Value:     0,
+							},
+							{
+								Timestamp: 2,
+								Value:     0,
+							},
+						},
+					},
 					{
 						Labels: map[string]string{
 							"service_name": "redis",
@@ -365,6 +412,21 @@ func TestProcessResultsErrorRate(t *testing.T) {
 							},
 						},
 					},
+					{
+						Labels: map[string]string{
+							"service_name": "route",
+						},
+						Points: []v3.Point{
+							{
+								Timestamp: 1,
+								Value:     0,
+							},
+							{
+								Timestamp: 2,
+								Value:     0,
+							},
+						},
+					},
 				},
 			},
 		},
@@ -906,14 +968,7 @@ func TestFormula(t *testing.T) {
 					},
 				},
 			},
-			want: &v3.Result{},
+			want: &v3.Result{
-		},
-		{
-			name:       "Group keys on both sides are overlapping but do not match exactly",
-			expression: "A/B",
-			results: []*v3.Result{
-				{
-					QueryName: "A",
 				Series: []*v3.Series{
 					{
 						Labels: map[string]string{
@@ -923,23 +978,23 @@ func TestFormula(t *testing.T) {
 						Points: []v3.Point{
 							{
 								Timestamp: 1,
-									Value:     10,
+								Value:     math.Inf(0),
 							},
 							{
 								Timestamp: 2,
-									Value:     20,
+								Value:     math.Inf(0),
 							},
 							{
 								Timestamp: 4,
-									Value:     40,
+								Value:     math.Inf(0),
 							},
 							{
 								Timestamp: 5,
-									Value:     50,
+								Value:     math.Inf(0),
 							},
 							{
 								Timestamp: 7,
-									Value:     70,
+								Value:     math.Inf(0),
 							},
 						},
 					},
@@ -951,88 +1006,81 @@ func TestFormula(t *testing.T) {
 						Points: []v3.Point{
 							{
 								Timestamp: 1,
-									Value:     12,
+								Value:     math.Inf(0),
 							},
 							{
 								Timestamp: 2,
-									Value:     45,
+								Value:     math.Inf(0),
 							},
 							{
 								Timestamp: 3,
-									Value:     30,
+								Value:     math.Inf(0),
 							},
 							{
 								Timestamp: 4,
-									Value:     40,
+								Value:     math.Inf(0),
 							},
 							{
 								Timestamp: 5,
-									Value:     50,
+								Value:     math.Inf(0),
 							},
 						},
 					},
-					},
-				},
-				{
-					QueryName: "B",
-					Series: []*v3.Series{
 					{
 						Labels: map[string]string{
-								"os.type": "linux",
+							"host_name": "ip-10-420-69-1",
-								"state":   "running",
+							"state":     "not_running_chalamet",
 						},
 						Points: []v3.Point{
 							{
 								Timestamp: 1,
-									Value:     22,
+								Value:     0,
 							},
 							{
 								Timestamp: 2,
-									Value:     65,
+								Value:     0,
 							},
 							{
 								Timestamp: 3,
-									Value:     30,
+								Value:     0,
 							},
 							{
 								Timestamp: 4,
-									Value:     40,
+								Value:     0,
 							},
 							{
 								Timestamp: 5,
-									Value:     50,
+								Value:     0,
 							},
 						},
 					},
 					{
 						Labels: map[string]string{
-								"os.type": "windows",
+							"host_name": "ip-10-420-69-2",
 							"state":     "busy",
 						},
 						Points: []v3.Point{
 							{
 								Timestamp: 1,
-									Value:     22,
+								Value:     0,
 							},
 							{
 								Timestamp: 2,
-									Value:     65,
+								Value:     0,
 							},
 							{
 								Timestamp: 4,
-									Value:     40,
+								Value:     0,
 							},
 							{
 								Timestamp: 5,
-									Value:     50,
+								Value:     0,
 							},
 						},
 					},
 				},
 			},
 		},
-			want: &v3.Result{},
-		},
 		{
 			name:       "Group keys on the left side are a superset of the right side",
 			expression: "A/B",
@@ -1193,6 +1241,59 @@ func TestFormula(t *testing.T) {
 							},
 						},
 					},
+					{
+						Labels: map[string]string{
+							"host_name": "ip-10-420-69-2",
+							"state":     "idle",
+							"os.type":   "linux",
+						},
+						Points: []v3.Point{
+							{
+								Timestamp: 1,
+								Value:     math.Inf(0),
+							},
+							{
+								Timestamp: 2,
+								Value:     math.Inf(0),
+							},
+							{
+								Timestamp: 3,
+								Value:     math.Inf(0),
+							},
+							{
+								Timestamp: 4,
+								Value:     math.Inf(0),
+							},
+							{
+								Timestamp: 5,
+								Value:     math.Inf(0),
+							},
+						},
+					},
+					{
+						Labels: map[string]string{
+							"state":   "busy",
+							"os.type": "linux",
+						},
+						Points: []v3.Point{
+							{
+								Timestamp: 1,
+								Value:     0,
+							},
+							{
+								Timestamp: 2,
+								Value:     0,
+							},
+							{
+								Timestamp: 4,
+								Value:     0,
+							},
+							{
+								Timestamp: 5,
+								Value:     0,
+							},
+						},
+					},
 				},
 			},
 		},
@@ -1454,18 +1555,22 @@ func TestFormula(t *testing.T) {
 			expression, err := govaluate.NewEvaluableExpression(tt.expression)
 			if err != nil {
 				t.Errorf("Error parsing expression: %v", err)
+				return
 			}
 			got, err := processResults(tt.results, expression)
 			if err != nil {
 				t.Errorf("Error processing results: %v", err)
+				return
 			}
 			if len(got.Series) != len(tt.want.Series) {
 				t.Errorf("processResults(): number of series - got = %v, want %v", len(got.Series), len(tt.want.Series))
+				return
 			}
 
 			for i := range got.Series {
 				if len(got.Series[i].Points) != len(tt.want.Series[i].Points) {
 					t.Errorf("processResults(): number of points - got = %v, want %v", len(got.Series[i].Points), len(tt.want.Series[i].Points))
+					return
 				}
 				for j := range got.Series[i].Points {
 					if got.Series[i].Points[j].Value != tt.want.Series[i].Points[j].Value {