Merge pull request #13782 from colega/improve-stringlabels-compare

Improve `Labels.Compare()` performance with `stringlabels`

model/labels/labels_stringlabels.go

@@ -363,13 +363,11 @@ func Compare(a, b Labels) int {
 
 	// Now we know that there is some difference before the end of a and b.
 	// Go back through the fields and find which field that difference is in.
-	firstCharDifferent := i
-	for i = 0; ; {
-		size, nextI := decodeSize(a.data, i)
-		if nextI+size > firstCharDifferent {
-			break
-		}
+	firstCharDifferent, i := i, 0
+	size, nextI := decodeSize(a.data, i)
+	for nextI+size <= firstCharDifferent {
 		i = nextI + size
+		size, nextI = decodeSize(a.data, i)
 	}
 	// Difference is inside this entry.
 	aStr, _ := decodeString(a.data, i)

model/labels/labels_test.go

@@ -532,6 +532,16 @@ var comparisonBenchmarkScenarios = []struct {
 		FromStrings("aaa", "bbb", "ccc", "ddd", "eee", "fff", "ggg", "hhh", "iii", "jjj", "kkk", "lll", "mmm", "nnn", "ooo", "ppp", "qqq", "rrz"),
 		FromStrings("aaa", "bbb", "ccc", "ddd", "eee", "fff", "ggg", "hhh", "iii", "jjj", "kkk", "lll", "mmm", "nnn", "ooo", "ppp", "qqq", "rrr"),
 	},
+	{
+		"real long equal",
+		FromStrings("__name__", "kube_pod_container_status_last_terminated_exitcode", "cluster", "prod-af-north-0", " container", "prometheus", "instance", "kube-state-metrics-0:kube-state-metrics:ksm", "job", "kube-state-metrics/kube-state-metrics", " namespace", "observability-prometheus", "pod", "observability-prometheus-0", "uid", "d3ec90b2-4975-4607-b45d-b9ad64bb417e"),
+		FromStrings("__name__", "kube_pod_container_status_last_terminated_exitcode", "cluster", "prod-af-north-0", " container", "prometheus", "instance", "kube-state-metrics-0:kube-state-metrics:ksm", "job", "kube-state-metrics/kube-state-metrics", " namespace", "observability-prometheus", "pod", "observability-prometheus-0", "uid", "d3ec90b2-4975-4607-b45d-b9ad64bb417e"),
+	},
+	{
+		"real long different end",
+		FromStrings("__name__", "kube_pod_container_status_last_terminated_exitcode", "cluster", "prod-af-north-0", " container", "prometheus", "instance", "kube-state-metrics-0:kube-state-metrics:ksm", "job", "kube-state-metrics/kube-state-metrics", " namespace", "observability-prometheus", "pod", "observability-prometheus-0", "uid", "d3ec90b2-4975-4607-b45d-b9ad64bb417e"),
+		FromStrings("__name__", "kube_pod_container_status_last_terminated_exitcode", "cluster", "prod-af-north-0", " container", "prometheus", "instance", "kube-state-metrics-0:kube-state-metrics:ksm", "job", "kube-state-metrics/kube-state-metrics", " namespace", "observability-prometheus", "pod", "observability-prometheus-0", "uid", "deadbeef-0000-1111-2222-b9ad64bb417e"),
+	},
 }
 
 func BenchmarkLabels_Equals(b *testing.B) {