update unit tests for slice samples

Signed-off-by: Ben Ye <benye@amazon.com>

Author: yeya24

pkg/querier/tripperware/instantquery/instant_query.go

@@ -340,7 +340,7 @@ func matrixMerge(resps []*PrometheusInstantQueryResponse) *Matrix {
 		if resp == nil {
 			continue
 		}
-		// Merge vector result samples only. Skip other types such as
+		// Merge matrix result samples only. Skip other types such as
 		// string, scalar as those are not sharable.
 		if resp.Data.Result.GetMatrix() == nil {
 			continue

pkg/querier/tripperware/util.go

@@ -2,12 +2,12 @@ package tripperware
 
 import (
 	"context"
-	"github.com/cortexproject/cortex/pkg/cortexpb"
 	"net/http"
 	"sort"
 
 	"github.com/weaveworks/common/httpgrpc"
 
+	"github.com/cortexproject/cortex/pkg/cortexpb"
 	"github.com/cortexproject/cortex/pkg/tenant"
 	"github.com/cortexproject/cortex/pkg/util/validation"
 )
@@ -77,8 +77,9 @@ func DoRequests(ctx context.Context, downstream Handler, reqs []Request, limits
 // return a sub slice whose first element's is the smallest timestamp that is strictly
 // bigger than the given minTs. Empty slice is returned if minTs is bigger than all the
 // timestamps in samples.
+// If the given samples slice is not sorted then unexpected samples would be returned.
 func SliceSamples(samples []cortexpb.Sample, minTs int64) []cortexpb.Sample {
-	if len(samples) <= 0 || minTs < samples[0].TimestampMs {
+	if len(samples) == 0 || minTs < samples[0].TimestampMs {
 		return samples
 	}
 

pkg/querier/tripperware/util_test.go

@@ -0,0 +1,83 @@
+package tripperware
+
+import (
+	"github.com/cortexproject/cortex/pkg/cortexpb"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestSliceSamples(t *testing.T) {
+	for _, tc := range []struct {
+		name            string
+		samples         []cortexpb.Sample
+		minTs           int64
+		expectedSamples []cortexpb.Sample
+	}{
+		{
+			name:            "empty samples",
+			samples:         nil,
+			expectedSamples: nil,
+		},
+		{
+			name: "minTs smaller than first sample's timestamp",
+			samples: []cortexpb.Sample{
+				{Value: 0, TimestampMs: 1},
+			},
+			minTs: 0,
+			expectedSamples: []cortexpb.Sample{
+				{Value: 0, TimestampMs: 1},
+			},
+		},
+		{
+			name: "input samples are not sorted, return all samples",
+			samples: []cortexpb.Sample{
+				{Value: 0, TimestampMs: 3}, {Value: 0, TimestampMs: 1},
+			},
+			minTs: 2,
+			expectedSamples: []cortexpb.Sample{
+				{Value: 0, TimestampMs: 3}, {Value: 0, TimestampMs: 1},
+			},
+		},
+		{
+			name: "minTs greater than the last sample's timestamp",
+			samples: []cortexpb.Sample{
+				{Value: 0, TimestampMs: 1}, {Value: 0, TimestampMs: 2},
+			},
+			minTs:           3,
+			expectedSamples: []cortexpb.Sample{},
+		},
+		{
+			name: "input samples not sorted, minTs greater than the last sample's timestamp",
+			samples: []cortexpb.Sample{
+				{Value: 0, TimestampMs: 0}, {Value: 0, TimestampMs: 3}, {Value: 0, TimestampMs: 1},
+			},
+			minTs:           2,
+			expectedSamples: []cortexpb.Sample{},
+		},
+		{
+			name: "input samples are sorted",
+			samples: []cortexpb.Sample{
+				{Value: 0, TimestampMs: 2}, {Value: 0, TimestampMs: 3}, {Value: 0, TimestampMs: 4},
+			},
+			minTs: 1,
+			expectedSamples: []cortexpb.Sample{
+				{Value: 0, TimestampMs: 2}, {Value: 0, TimestampMs: 3}, {Value: 0, TimestampMs: 4},
+			},
+		},
+		{
+			name: "input samples are sorted, get sliced samples",
+			samples: []cortexpb.Sample{
+				{Value: 0, TimestampMs: 1}, {Value: 0, TimestampMs: 2}, {Value: 0, TimestampMs: 3},
+			},
+			minTs: 2,
+			expectedSamples: []cortexpb.Sample{
+				{Value: 0, TimestampMs: 3},
+			},
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			actual := SliceSamples(tc.samples, tc.minTs)
+			assert.Equal(t, tc.expectedSamples, actual)
+		})
+	}
+}