diff --git a/promql/engine.go b/promql/engine.go
index 8756f15c6c..fce5321ef8 100644
--- a/promql/engine.go
+++ b/promql/engine.go
@@ -108,20 +108,20 @@ func (s Point) String() string {
 	return ""
 }
 
-// sample is a single sample belonging to a COWMetric.
-type sample struct {
+// Sample is a single sample belonging to a metric.
+type Sample struct {
 	Point
 
 	Metric labels.Labels
 }
 
-func (s sample) String() string {
+func (s Sample) String() string {
 	return ""
 }
 
 // Vector is basically only an alias for model.Samples, but the
 // contract is that in a Vector, all Samples have the same timestamp.
-type Vector []sample
+type Vector []Sample
 
 func (vec Vector) String() string {
 	entries := make([]string, len(vec))
@@ -804,7 +804,7 @@ func (ev *evaluator) VectorSelector(node *VectorSelector) Vector {
 			}
 		}
 
-		vec = append(vec, sample{
+		vec = append(vec, Sample{
 			Metric: node.series[i].Labels(),
 			Point:  Point{V: v, T: ev.Timestamp},
 		})
@@ -936,7 +936,7 @@ func (ev *evaluator) VectorBinop(op itemType, lhs, rhs Vector, matching *VectorM
 	}
 
 	// All samples from the rhs hashed by the matching label/values.
-	rightSigs := map[uint64]sample{}
+	rightSigs := map[uint64]Sample{}
 
 	// Add all rhs samples to a map so we can easily find matches later.
 	for _, rs := range rhs {
@@ -1002,7 +1002,7 @@ func (ev *evaluator) VectorBinop(op itemType, lhs, rhs Vector, matching *VectorM
 			insertedSigs[insertSig] = struct{}{}
 		}
 
-		result = append(result, sample{
+		result = append(result, Sample{
 			Metric: metric,
 			Point:  Point{V: value, T: ev.Timestamp},
 		})
@@ -1310,13 +1310,13 @@ func (ev *evaluator) aggregation(op itemType, grouping []string, without bool, k
 			}
 			if op == itemTopK || op == itemQuantile {
 				result[groupingKey].heap = make(VectorByValueHeap, 0, k)
-				heap.Push(&result[groupingKey].heap, &sample{
+				heap.Push(&result[groupingKey].heap, &Sample{
 					Point:  Point{V: s.V},
 					Metric: s.Metric,
 				})
 			} else if op == itemBottomK {
 				result[groupingKey].reverseHeap = make(VectorByReverseValueHeap, 0, k)
-				heap.Push(&result[groupingKey].reverseHeap, &sample{
+				heap.Push(&result[groupingKey].reverseHeap, &Sample{
 					Point:  Point{V: s.V},
 					Metric: s.Metric,
 				})
@@ -1359,7 +1359,7 @@ func (ev *evaluator) aggregation(op itemType, grouping []string, without bool, k
 				if int64(len(group.heap)) == k {
 					heap.Pop(&group.heap)
 				}
-				heap.Push(&group.heap, &sample{
+				heap.Push(&group.heap, &Sample{
 					Point:  Point{V: s.V},
 					Metric: s.Metric,
 				})
@@ -1370,7 +1370,7 @@ func (ev *evaluator) aggregation(op itemType, grouping []string, without bool, k
 				if int64(len(group.reverseHeap)) == k {
 					heap.Pop(&group.reverseHeap)
 				}
-				heap.Push(&group.reverseHeap, &sample{
+				heap.Push(&group.reverseHeap, &Sample{
 					Point:  Point{V: s.V},
 					Metric: s.Metric,
 				})
@@ -1407,7 +1407,7 @@ func (ev *evaluator) aggregation(op itemType, grouping []string, without bool, k
 			// The heap keeps the lowest value on top, so reverse it.
 			sort.Sort(sort.Reverse(aggr.heap))
 			for _, v := range aggr.heap {
-				resultVector = append(resultVector, sample{
+				resultVector = append(resultVector, Sample{
 					Metric: v.Metric,
 					Point:  Point{V: v.V, T: ev.Timestamp},
 				})
@@ -1418,7 +1418,7 @@ func (ev *evaluator) aggregation(op itemType, grouping []string, without bool, k
 			// The heap keeps the lowest value on top, so reverse it.
 			sort.Sort(sort.Reverse(aggr.reverseHeap))
 			for _, v := range aggr.reverseHeap {
-				resultVector = append(resultVector, sample{
+				resultVector = append(resultVector, Sample{
 					Metric: v.Metric,
 					Point:  Point{V: v.V, T: ev.Timestamp},
 				})
@@ -1432,7 +1432,7 @@ func (ev *evaluator) aggregation(op itemType, grouping []string, without bool, k
 			// For other aggregations, we already have the right value.
 		}
 
-		resultVector = append(resultVector, sample{
+		resultVector = append(resultVector, Sample{
 			Metric: aggr.labels,
 			Point:  Point{V: aggr.value, T: ev.Timestamp},
 		})
diff --git a/promql/functions.go b/promql/functions.go
index fdcc62937f..27ac1d40ea 100644
--- a/promql/functions.go
+++ b/promql/functions.go
@@ -116,7 +116,7 @@ func extrapolatedRate(ev *evaluator, arg Expr, isCounter bool, isRate bool) Valu
 			resultValue = resultValue / 1000 / ms.Range.Seconds()
 		}
 
-		resultVector = append(resultVector, sample{
+		resultVector = append(resultVector, Sample{
 			Metric: copyLabels(samples.Metric, false),
 			Point:  Point{V: resultValue, T: ev.Timestamp},
 		})
@@ -179,7 +179,7 @@ func instantValue(ev *evaluator, arg Expr, isRate bool) Value {
 			resultValue /= float64(sampledInterval) / 1000
 		}
 
-		resultVector = append(resultVector, sample{
+		resultVector = append(resultVector, Sample{
 			Metric: copyLabels(samples.Metric, false),
 			Point:  Point{V: resultValue, T: ev.Timestamp},
 		})
@@ -272,7 +272,7 @@ func funcHoltWinters(ev *evaluator, args Expressions) Value {
 			s[i] = x + y
 		}
 
-		resultVector = append(resultVector, sample{
+		resultVector = append(resultVector, Sample{
 			Metric: copyLabels(samples.Metric, false),
 			Point:  Point{V: s[len(s)-1], T: ev.Timestamp}, // The last value in the Vector is the smoothed result.
 		})
@@ -413,7 +413,7 @@ func aggrOverTime(ev *evaluator, args Expressions, aggrFn func([]Point) float64)
 			continue
 		}
 
-		resultVector = append(resultVector, sample{
+		resultVector = append(resultVector, Sample{
 			Metric: copyLabels(el.Metric, false),
 			Point:  Point{V: aggrFn(el.Points), T: ev.Timestamp},
 		})
@@ -496,9 +496,9 @@ func funcQuantileOverTime(ev *evaluator, args Expressions) Value {
 		el.Metric = copyLabels(el.Metric, false)
 		values := make(VectorByValueHeap, 0, len(el.Points))
 		for _, v := range el.Points {
-			values = append(values, sample{Point: Point{V: v.V}})
+			values = append(values, Sample{Point: Point{V: v.V}})
 		}
-		resultVector = append(resultVector, sample{
+		resultVector = append(resultVector, Sample{
 			Metric: el.Metric,
 			Point:  Point{V: quantile(q, values), T: ev.Timestamp},
 		})
@@ -559,7 +559,7 @@ func funcAbsent(ev *evaluator, args Expressions) Value {
 		}
 	}
 	return Vector{
-		sample{
+		Sample{
 			Metric: labels.New(m...),
 			Point:  Point{V: 1, T: ev.Timestamp},
 		},
@@ -663,7 +663,7 @@ func funcDeriv(ev *evaluator, args Expressions) Value {
 			continue
 		}
 		slope, _ := linearRegression(samples.Points, 0)
-		resultSample := sample{
+		resultSample := Sample{
 			Metric: copyLabels(samples.Metric, false),
 			Point:  Point{V: slope, T: ev.Timestamp},
 		}
@@ -687,7 +687,7 @@ func funcPredictLinear(ev *evaluator, args Expressions) Value {
 		}
 		slope, intercept := linearRegression(samples.Points, ev.Timestamp)
 
-		resultVector = append(resultVector, sample{
+		resultVector = append(resultVector, Sample{
 			Metric: copyLabels(samples.Metric, false),
 			Point:  Point{V: slope*duration + intercept, T: ev.Timestamp},
 		})
@@ -727,7 +727,7 @@ func funcHistogramQuantile(ev *evaluator, args Expressions) Value {
 	}
 
 	for _, mb := range signatureToMetricWithBuckets {
-		outVec = append(outVec, sample{
+		outVec = append(outVec, Sample{
 			Metric: mb.metric,
 			Point:  Point{V: bucketQuantile(q, mb.buckets), T: ev.Timestamp},
 		})
@@ -752,7 +752,7 @@ func funcResets(ev *evaluator, args Expressions) Value {
 			prev = current
 		}
 
-		out = append(out, sample{
+		out = append(out, Sample{
 			Metric: copyLabels(samples.Metric, false),
 			Point:  Point{V: float64(resets), T: ev.Timestamp},
 		})
@@ -776,7 +776,7 @@ func funcChanges(ev *evaluator, args Expressions) Value {
 			prev = current
 		}
 
-		out = append(out, sample{
+		out = append(out, Sample{
 			Metric: copyLabels(samples.Metric, false),
 			Point:  Point{V: float64(changes), T: ev.Timestamp},
 		})
@@ -832,7 +832,7 @@ func funcLabelReplace(ev *evaluator, args Expressions) Value {
 // === Vector(s Scalar) Vector ===
 func funcVector(ev *evaluator, args Expressions) Value {
 	return Vector{
-		sample{
+		Sample{
 			Metric: labels.Labels{},
 			Point:  Point{V: ev.evalFloat(args[0]), T: ev.Timestamp},
 		},
@@ -844,7 +844,7 @@ func dateWrapper(ev *evaluator, args Expressions, f func(time.Time) float64) Val
 	var v Vector
 	if len(args) == 0 {
 		v = Vector{
-			sample{
+			Sample{
 				Metric: labels.Labels{},
 				Point:  Point{V: float64(ev.Timestamp) / 1000},
 			},
@@ -1220,7 +1220,7 @@ func (s VectorByValueHeap) Swap(i, j int) {
 }
 
 func (s *VectorByValueHeap) Push(x interface{}) {
-	*s = append(*s, x.(sample))
+	*s = append(*s, x.(Sample))
 }
 
 func (s *VectorByValueHeap) Pop() interface{} {
@@ -1249,7 +1249,7 @@ func (s VectorByReverseValueHeap) Swap(i, j int) {
 }
 
 func (s *VectorByReverseValueHeap) Push(x interface{}) {
-	*s = append(*s, x.(sample))
+	*s = append(*s, x.(Sample))
 }
 
 func (s *VectorByReverseValueHeap) Pop() interface{} {