MQE: don't select more data than strictly necessary (#10209)

pkg/streamingpromql/operators/selectors/selector.go

@@ -57,7 +57,7 @@ func (s *Selector) SeriesMetadata(ctx context.Context) ([]types.SeriesMetadata,
 
 	// Apply lookback delta, range and offset after adjusting for timestamp from @ modifier.
 	rangeMilliseconds := s.Range.Milliseconds()
-	startTimestamp = startTimestamp - s.LookbackDelta.Milliseconds() - rangeMilliseconds - s.Offset - 1 // -1 to exclude samples on the lower boundary of the range.
+	startTimestamp = startTimestamp - s.LookbackDelta.Milliseconds() - rangeMilliseconds - s.Offset + 1 // +1 to exclude samples on the lower boundary of the range (queriers work with closed intervals, we use left-open).
 	endTimestamp = endTimestamp - s.Offset
 
 	hints := &storage.SelectHints{

pkg/streamingpromql/operators/selectors/selector_test.go

@@ -3,13 +3,17 @@
 package selectors
 
 import (
+	"context"
 	"fmt"
 	"strconv"
 	"testing"
+	"time"
 
 	"github.com/prometheus/prometheus/model/labels"
+	"github.com/prometheus/prometheus/model/timestamp"
 	"github.com/prometheus/prometheus/storage"
 	"github.com/prometheus/prometheus/tsdb/chunkenc"
+	"github.com/prometheus/prometheus/util/annotations"
 	"github.com/stretchr/testify/require"
 
 	"github.com/grafana/mimir/pkg/streamingpromql/types"
@@ -97,3 +101,83 @@ func (m mockSeries) Labels() labels.Labels {
 func (m mockSeries) Iterator(chunkenc.Iterator) chunkenc.Iterator {
 	panic("mockSeries: Iterator() not supported")
 }
+
+func TestSelector_QueryRanges(t *testing.T) {
+	start := time.Date(2024, 12, 11, 3, 12, 45, 0, time.UTC)
+	end := start.Add(time.Hour)
+	timeRange := types.NewRangeQueryTimeRange(start, end, time.Minute)
+
+	t.Run("instant vector selector", func(t *testing.T) {
+		queryable := &mockQueryable{}
+		lookbackDelta := 5 * time.Minute
+		s := &Selector{
+			Queryable:     queryable,
+			TimeRange:     timeRange,
+			LookbackDelta: lookbackDelta,
+		}
+
+		_, err := s.SeriesMetadata(context.Background())
+		require.NoError(t, err)
+
+		expectedMinT := timestamp.FromTime(start.Add(-lookbackDelta).Add(time.Millisecond)) // Add a millisecond to exclude the beginning of the range.
+		expectedMaxT := timestamp.FromTime(end)
+		require.Equal(t, expectedMinT, queryable.mint)
+		require.Equal(t, expectedMaxT, queryable.maxt)
+		require.Equal(t, expectedMinT, queryable.hints.Start)
+		require.Equal(t, expectedMaxT, queryable.hints.End)
+	})
+
+	t.Run("range vector selector", func(t *testing.T) {
+		queryable := &mockQueryable{}
+		selectorRange := 15 * time.Minute
+		s := &Selector{
+			Queryable: queryable,
+			TimeRange: timeRange,
+			Range:     selectorRange,
+		}
+
+		_, err := s.SeriesMetadata(context.Background())
+		require.NoError(t, err)
+
+		expectedMinT := timestamp.FromTime(start.Add(-selectorRange).Add(time.Millisecond)) // Add a millisecond to exclude the beginning of the range.
+		expectedMaxT := timestamp.FromTime(end)
+		require.Equal(t, expectedMinT, queryable.mint)
+		require.Equal(t, expectedMaxT, queryable.maxt)
+		require.Equal(t, expectedMinT, queryable.hints.Start)
+		require.Equal(t, expectedMaxT, queryable.hints.End)
+	})
+}
+
+type mockQueryable struct {
+	mint, maxt int64
+	hints      *storage.SelectHints
+}
+
+func (m *mockQueryable) Querier(mint, maxt int64) (storage.Querier, error) {
+	m.mint = mint
+	m.maxt = maxt
+
+	return &mockQuerier{m}, nil
+}
+
+type mockQuerier struct {
+	q *mockQueryable
+}
+
+func (m *mockQuerier) Select(_ context.Context, _ bool, hints *storage.SelectHints, _ ...*labels.Matcher) storage.SeriesSet {
+	m.q.hints = hints
+
+	return storage.EmptySeriesSet()
+}
+
+func (m *mockQuerier) LabelValues(context.Context, string, *storage.LabelHints, ...*labels.Matcher) ([]string, annotations.Annotations, error) {
+	panic("not supported")
+}
+
+func (m *mockQuerier) LabelNames(context.Context, *storage.LabelHints, ...*labels.Matcher) ([]string, annotations.Annotations, error) {
+	panic("not supported")
+}
+
+func (m *mockQuerier) Close() error {
+	panic("not supported")
+}