func writeRandomTimeSeriesDataToRange(
	t testing.TB,
	store *storage.Store,
	rangeID roachpb.RangeID,
	keyPrefix []byte,
) (midpoint []byte) {
	src := rand.New(rand.NewSource(0))
	r := ts.Resolution10s
	for i := 0; i < 20; i++ {
		var data []tspb.TimeSeriesData
		for j := int64(0); j <= src.Int63n(5); j++ {
			d := tspb.TimeSeriesData{
				Name:   "test.random.metric",
				Source: "cpu01",
			}
			for k := int64(0); k <= src.Int63n(10); k++ {
				d.Datapoints = append(d.Datapoints, tspb.TimeSeriesDatapoint{
					TimestampNanos: src.Int63n(200) * r.KeyDuration(),
					Value:          src.Float64(),
				})
			}
			data = append(data, d)
		}
		for _, d := range data {
			idatas, err := d.ToInternal(r.KeyDuration(), r.SampleDuration())
			if err != nil {
				t.Fatal(err)
			}
			for _, idata := range idatas {
				var value roachpb.Value
				if err := value.SetProto(&idata); err != nil {
					t.Fatal(err)
				}
				mArgs := roachpb.MergeRequest{
					Span: roachpb.Span{
						Key: encoding.EncodeVarintAscending(keyPrefix, idata.StartTimestampNanos),
					},
					Value: value,
				}
				if _, pErr := client.SendWrappedWith(rg1(store), nil, roachpb.Header{
					RangeID: rangeID,
				}, &mArgs); pErr != nil {
					t.Fatal(pErr)
				}
			}
		}
	}
	// Return approximate midway point (100 is midway between random timestamps in range [0,200)).
	midKey := append([]byte(nil), keyPrefix...)
	midKey = encoding.EncodeVarintAscending(midKey, 100*r.KeyDuration())
	return keys.MakeRowSentinelKey(midKey)
}