Remove mapPoints() utility (#175)

Signed-off-by: Marco Pracucci <marco@pracucci.com>

pkg/mimirpb/compat.go

@@ -20,6 +20,7 @@ import (
 	"github.com/prometheus/prometheus/pkg/exemplar"
 	"github.com/prometheus/prometheus/pkg/labels"
 	"github.com/prometheus/prometheus/pkg/textparse"
+	"github.com/prometheus/prometheus/promql"
 
 	"github.com/grafana/mimir/pkg/util"
 )
@@ -146,6 +147,11 @@ func FromExemplarProtosToExemplars(es []Exemplar) []exemplar.Exemplar {
 	return result
 }
 
+// FromPointsToSamples casts []promql.Point to []Sample. It uses unsafe.
+func FromPointsToSamples(points []promql.Point) []Sample {
+	return *(*[]Sample)(unsafe.Pointer(&points))
+}
+
 type byLabel []LabelAdapter
 
 func (s byLabel) Len() int           { return len(s) }

pkg/mimirpb/compat_test.go

@@ -15,6 +15,7 @@ import (
 	jsoniter "github.com/json-iterator/go"
 	"github.com/prometheus/prometheus/pkg/labels"
 	"github.com/prometheus/prometheus/pkg/textparse"
+	"github.com/prometheus/prometheus/promql"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -142,3 +143,10 @@ func BenchmarkFromLabelAdaptersToLabelsWithCopy(b *testing.B) {
 		FromLabelAdaptersToLabelsWithCopy(input)
 	}
 }
+
+func TestFromPointsToSamples(t *testing.T) {
+	input := []promql.Point{{T: 1, V: 2}, {T: 3, V: 4}}
+	expected := []Sample{{TimestampMs: 1, Value: 2}, {TimestampMs: 3, Value: 4}}
+
+	assert.Equal(t, expected, FromPointsToSamples(input))
+}

pkg/mimirpb/mimir.proto

@@ -41,8 +41,9 @@ message LabelPair {
 }
 
 message Sample {
-  double value       = 1;
+  // Fields order MUST match promql.Point so that we can cast types between them.
   int64 timestamp_ms = 2;
+  double value       = 1;
 }
 
 message MetricMetadata {

pkg/querier/queryrange/value.go

@@ -41,8 +41,11 @@ func FromResult(res *promql.Result) ([]SampleStream, error) {
 		res := make([]SampleStream, 0, len(v))
 		for _, sample := range v {
 			res = append(res, SampleStream{
-				Labels:  mapLabels(sample.Metric),
-				Samples: mapPoints(sample.Point),
+				Labels: mapLabels(sample.Metric),
+				Samples: []mimirpb.Sample{{
+					TimestampMs: sample.Point.T,
+					Value:       sample.Point.V,
+				}},
 			})
 		}
 		return res, nil
@@ -52,7 +55,7 @@ func FromResult(res *promql.Result) ([]SampleStream, error) {
 		for _, series := range v {
 			res = append(res, SampleStream{
 				Labels:  mapLabels(series.Metric),
-				Samples: mapPoints(series.Points...),
+				Samples: mimirpb.FromPointsToSamples(series.Points),
 			})
 		}
 		return res, nil
@@ -71,19 +74,6 @@ func mapLabels(ls labels.Labels) []mimirpb.LabelAdapter {
 	return result
 }
 
-func mapPoints(pts ...promql.Point) []mimirpb.Sample {
-	result := make([]mimirpb.Sample, 0, len(pts))
-
-	for _, pt := range pts {
-		result = append(result, mimirpb.Sample{
-			Value:       pt.V,
-			TimestampMs: pt.T,
-		})
-	}
-
-	return result
-}
-
 // ResponseToSamples is needed to map back from api response to the underlying series data
 func ResponseToSamples(resp Response) ([]SampleStream, error) {
 	promRes, ok := resp.(*PrometheusResponse)