From 41ecb6c6b2df1e3e2e1dbbe57524445ec015350d Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@soundcloud.com>
Date: Tue, 5 May 2015 22:16:17 +0200
Subject: [PATCH] Improve the Metric.Equal and Metric.Before methods.

---
 model/metric.go      | 64 +++++++++++++++++++++++++++++++++++++++-----
 model/sample_test.go | 60 +++++++++++++++++------------------------
 model/signature.go   |  2 +-
 3 files changed, 83 insertions(+), 43 deletions(-)

diff --git a/model/metric.go b/model/metric.go
index b43ddaf..0870f23 100644
--- a/model/metric.go
+++ b/model/metric.go
@@ -26,16 +26,68 @@ var separator = []byte{0}
 // a singleton and refers to one and only one stream of samples.
 type Metric map[LabelName]LabelValue
 
-// Equal compares the fingerprints of both metrics.
+// Equal compares the metrics.
 func (m Metric) Equal(o Metric) bool {
-	// TODO do an actual map comparison
-	return m.Fingerprint().Equal(o.Fingerprint())
+	if len(m) != len(o) {
+		return false
+	}
+	for ln, lv := range m {
+		olv, ok := o[ln]
+		if !ok {
+			return false
+		}
+		if olv != lv {
+			return false
+		}
+	}
+	return true
 }
 
-// Before compares the fingerprints of both metrics.
+// Before compares the metrics, using the following criteria:
+//
+// If m has fewer labels than o, it is before o. If it has more, it is not.
+//
+// If the number of labels is the same, the superset of all label names is
+// sorted alphanumerically. The first differing label pair found in that order
+// determines the outcome: If the label does not exist at all in m, then m is
+// before o, and vice versa. Otherwise the label value is compared
+// alphanumerically.
+//
+// If m and o are equal, the method returns false.
 func (m Metric) Before(o Metric) bool {
-	// TODO do an actual map comparison
-	return m.Fingerprint().Less(o.Fingerprint())
+	if len(m) < len(o) {
+		return true
+	}
+	if len(m) > len(o) {
+		return false
+	}
+
+	lns := make(LabelNames, 0, len(m)+len(o))
+	for ln := range m {
+		lns = append(lns, ln)
+	}
+	for ln := range o {
+		lns = append(lns, ln)
+	}
+	// It's probably not worth it to de-dup lns.
+	sort.Sort(lns)
+	for _, ln := range lns {
+		mlv, ok := m[ln]
+		if !ok {
+			return true
+		}
+		olv, ok := o[ln]
+		if !ok {
+			return false
+		}
+		if mlv < olv {
+			return true
+		}
+		if mlv > olv {
+			return false
+		}
+	}
+	return false
 }
 
 // String implements Stringer.
diff --git a/model/sample_test.go b/model/sample_test.go
index 3dc4ad2..d5e065d 100644
--- a/model/sample_test.go
+++ b/model/sample_test.go
@@ -21,42 +21,36 @@ import (
 func TestSamplesSort(t *testing.T) {
 	input := Samples{
 		&Sample{
-			// Fingerprint: 81f9c9ed24563f8f.
 			Metric: Metric{
 				MetricNameLabel: "A",
 			},
 			Timestamp: 1,
 		},
 		&Sample{
-			// Fingerprint: 81f9c9ed24563f8f.
 			Metric: Metric{
 				MetricNameLabel: "A",
 			},
 			Timestamp: 2,
 		},
 		&Sample{
-			// Fingerprint: 1bf6c9ed24543f8f.
 			Metric: Metric{
 				MetricNameLabel: "C",
 			},
 			Timestamp: 1,
 		},
 		&Sample{
-			// Fingerprint: 1bf6c9ed24543f8f.
 			Metric: Metric{
 				MetricNameLabel: "C",
 			},
 			Timestamp: 2,
 		},
 		&Sample{
-			// Fingerprint: 68f4c9ed24533f8f.
 			Metric: Metric{
 				MetricNameLabel: "B",
 			},
 			Timestamp: 1,
 		},
 		&Sample{
-			// Fingerprint: 68f4c9ed24533f8f.
 			Metric: Metric{
 				MetricNameLabel: "B",
 			},
@@ -66,47 +60,41 @@ func TestSamplesSort(t *testing.T) {
 
 	expected := Samples{
 		&Sample{
-			// Fingerprint: 1bf6c9ed24543f8f.
-			Metric: Metric{
-				MetricNameLabel: "C",
-			},
-			Timestamp: 1,
-		},
-		&Sample{
-			// Fingerprint: 1bf6c9ed24543f8f.
-			Metric: Metric{
-				MetricNameLabel: "C",
-			},
-			Timestamp: 2,
-		},
-		&Sample{
-			// Fingerprint: 68f4c9ed24533f8f.
-			Metric: Metric{
-				MetricNameLabel: "B",
-			},
-			Timestamp: 1,
-		},
-		&Sample{
-			// Fingerprint: 68f4c9ed24533f8f.
-			Metric: Metric{
-				MetricNameLabel: "B",
-			},
-			Timestamp: 2,
-		},
-		&Sample{
-			// Fingerprint: 81f9c9ed24563f8f.
 			Metric: Metric{
 				MetricNameLabel: "A",
 			},
 			Timestamp: 1,
 		},
 		&Sample{
-			// Fingerprint: 81f9c9ed24563f8f.
 			Metric: Metric{
 				MetricNameLabel: "A",
 			},
 			Timestamp: 2,
 		},
+		&Sample{
+			Metric: Metric{
+				MetricNameLabel: "B",
+			},
+			Timestamp: 1,
+		},
+		&Sample{
+			Metric: Metric{
+				MetricNameLabel: "B",
+			},
+			Timestamp: 2,
+		},
+		&Sample{
+			Metric: Metric{
+				MetricNameLabel: "C",
+			},
+			Timestamp: 1,
+		},
+		&Sample{
+			Metric: Metric{
+				MetricNameLabel: "C",
+			},
+			Timestamp: 2,
+		},
 	}
 
 	sort.Sort(input)
diff --git a/model/signature.go b/model/signature.go
index 3f7abec..7bd58f4 100644
--- a/model/signature.go
+++ b/model/signature.go
@@ -52,7 +52,7 @@ func putHashAndBuf(hb *hashAndBuf) {
 	hashAndBufPool.Put(hb)
 }
 
-// LabelsToSignature returns an quasi-unique signature (i.e., fingerprint) for a
+// LabelsToSignature returns a quasi-unique signature (i.e., fingerprint) for a
 // given label set. (Collisions are possible but unlikely if the number of label
 // sets the function is applied to is small.)
 func LabelsToSignature(labels map[string]string) uint64 {