fix(stats): calculate mileage without previous-day baseline

go/vehicle-gateway/cmd/stats-backfill/main.go

@@ -74,8 +74,11 @@ type dailySourceLast struct {
 	Phone          string
 	DeviceID       string
 	SourceEndpoint string
+	FirstTS        time.Time
 	TS             time.Time
+	FirstTotalKM   float64
 	TotalKM        float64
+	RawSampleCount int64
 }
 
 func main() {
@@ -233,21 +236,17 @@ func addSamples(aggregates map[string]*metricAgg, samples []stats.MetricSample)
 				SourceEndpoint:  sample.SourceEndpoint,
 				FirstEventTime:  sample.EventTime,
 				LatestEventTime: sample.EventTime,
-				QualityStatus:   stats.QualityNoPreviousBaseline,
+				QualityStatus:   stats.QualityOK,
-				QualityReason:   "scan_backfill_missing_previous_source",
+				QualityReason:   "current_day_first_sample",
 			}
 			continue
 		}
-		if sample.TotalMileageKM < agg.FirstKM {
-			agg.FirstKM = sample.TotalMileageKM
-		}
-		if sample.TotalMileageKM > agg.LatestKM {
-			agg.LatestKM = sample.TotalMileageKM
-		}
 		if agg.FirstEventTime.IsZero() || sample.EventTime.Before(agg.FirstEventTime) {
+			agg.FirstKM = sample.TotalMileageKM
 			agg.FirstEventTime = sample.EventTime
 		}
 		if sample.EventTime.After(agg.LatestEventTime) {
+			agg.LatestKM = sample.TotalMileageKM
 			agg.LatestEventTime = sample.EventTime
 			agg.SourceEndpoint = sample.SourceEndpoint
 			if strings.TrimSpace(sample.Phone) != "" {
@@ -339,22 +338,6 @@ func clearBackfillTargetMileage(ctx context.Context, db *sql.DB, vin string, sta
 }
 
 func buildLastDiffAggregates(ctx context.Context, db *sql.DB, cfg config) (map[string]*metricAgg, error) {
-	dates, err := dateRangeWithPrevious(cfg.DateFrom, cfg.DateTo)
-	if err != nil {
-		return nil, err
-	}
-	lastByProtocolDate := map[envelope.Protocol]map[string]map[string][]dailySourceLast{}
-	for _, protocol := range cfg.Protocols {
-		lastByProtocolDate[protocol] = map[string]map[string][]dailySourceLast{}
-		for _, date := range dates {
-			rows, err := queryDailyLastSourceRows(ctx, db, cfg, protocol, date)
-			if err != nil {
-				return nil, err
-			}
-			lastByProtocolDate[protocol][date] = rows
-			slog.Info("daily last loaded", "protocol", protocol, "date", date, "vehicles", len(rows))
-		}
-	}
 	targetDates, err := dateRange(cfg.DateFrom, cfg.DateTo)
 	if err != nil {
 		return nil, err
@@ -362,9 +345,15 @@ func buildLastDiffAggregates(ctx context.Context, db *sql.DB, cfg config) (map[s
 	aggregates := map[string]*metricAgg{}
 	for _, protocol := range cfg.Protocols {
 		for _, date := range targetDates {
-			prevDate := previousDate(date)
+			current, err := queryDailyLastSourceRows(ctx, db, cfg, protocol, date)
-			current := lastByProtocolDate[protocol][date]
+			if err != nil {
-			previous := lastByProtocolDate[protocol][prevDate]
+				return nil, err
+			}
+			previous, err := queryPreviousLastSourceRows(ctx, db, cfg, protocol, date)
+			if err != nil {
+				return nil, err
+			}
+			slog.Info("daily last loaded", "protocol", protocol, "date", date, "vehicles", len(current), "previousVehicles", len(previous))
 			for vin, currentSources := range current {
 				previousBySource := map[string]dailySourceLast{}
 				for _, previousRow := range previous[vin] {
@@ -372,29 +361,8 @@ func buildLastDiffAggregates(ctx context.Context, db *sql.DB, cfg config) (map[s
 				}
 				for _, currentRow := range currentSources {
 					key := vin + "|" + date + "|" + string(protocol) + "|" + currentRow.SourceKey
-					agg := &metricAgg{
+					previousRow, hasPrevious := previousBySource[currentRow.SourceKey]
-						VIN:             vin,
+					aggregates[key] = aggregateFromDailySource(date, protocol, currentRow, previousRow, hasPrevious)
-						Date:            date,
-						Protocol:        protocol,
-						FirstKM:         currentRow.TotalKM,
-						LatestKM:        currentRow.TotalKM,
-						Count:           1,
-						SourceKey:       currentRow.SourceKey,
-						Phone:           currentRow.Phone,
-						DeviceID:        currentRow.DeviceID,
-						SourceEndpoint:  currentRow.SourceEndpoint,
-						FirstEventTime:  currentRow.TS,
-						LatestEventTime: currentRow.TS,
-						QualityStatus:   stats.QualityNoPreviousBaseline,
-						QualityReason:   "missing_previous_source",
-					}
-					if previousRow, ok := previousBySource[currentRow.SourceKey]; ok {
-						agg.FirstKM = previousRow.TotalKM
-						agg.FirstEventTime = previousRow.TS
-						agg.QualityStatus = stats.QualityOK
-						agg.QualityReason = "same_source_previous_day"
-					}
-					aggregates[key] = agg
 				}
 			}
 		}
@@ -402,6 +370,40 @@ func buildLastDiffAggregates(ctx context.Context, db *sql.DB, cfg config) (map[s
 	return aggregates, nil
 }
 
+func aggregateFromDailySource(date string, protocol envelope.Protocol, current dailySourceLast, previous dailySourceLast, hasPrevious bool) *metricAgg {
+	firstKM := current.FirstTotalKM
+	firstEventTime := current.FirstTS
+	qualityReason := "current_day_first_sample"
+	if hasPrevious {
+		firstKM = previous.TotalKM
+		firstEventTime = previous.TS
+		qualityReason = "historical_source_baseline"
+	}
+	if firstEventTime.IsZero() {
+		firstEventTime = current.TS
+	}
+	count := current.RawSampleCount
+	if count <= 0 {
+		count = 1
+	}
+	return &metricAgg{
+		VIN:             current.VIN,
+		Date:            date,
+		Protocol:        protocol,
+		FirstKM:         firstKM,
+		LatestKM:        current.TotalKM,
+		Count:           count,
+		SourceKey:       current.SourceKey,
+		Phone:           current.Phone,
+		DeviceID:        current.DeviceID,
+		SourceEndpoint:  current.SourceEndpoint,
+		FirstEventTime:  firstEventTime,
+		LatestEventTime: current.TS,
+		QualityStatus:   stats.QualityOK,
+		QualityReason:   qualityReason,
+	}
+}
+
 type trustedChoice struct {
 	current  dailySourceLast
 	previous dailySourceLast
@@ -443,10 +445,30 @@ func queryDailyLastSourceRows(ctx context.Context, db *sql.DB, cfg config, proto
 		fmt.Sprintf("protocol = '%s'", quote(string(protocol))),
 		realtimeMileageFramePredicate(),
 	}
-	sqlText := fmt.Sprintf(`SELECT vin, phone, device_id, source_endpoint, LAST(ts), LAST(parsed_json)
+	sqlText := fmt.Sprintf(`SELECT vin, phone, device_id, source_endpoint, FIRST(ts), FIRST(parsed_json), LAST(ts), LAST(parsed_json), COUNT(*)
 FROM %s.raw_frames
 WHERE %s
 GROUP BY vin, phone, device_id, source_endpoint`, ident(cfg.TDengineDatabase), strings.Join(where, " AND "))
+	return querySourceRows(ctx, db, cfg, protocol, sqlText, true)
+}
+
+func queryPreviousLastSourceRows(ctx context.Context, db *sql.DB, cfg config, protocol envelope.Protocol, date string) (map[string][]dailySourceLast, error) {
+	where := []string{
+		fmt.Sprintf("ts < '%s 00:00:00'", quote(date)),
+		"parse_status = 'OK'",
+		"vin IS NOT NULL",
+		"vin <> ''",
+		fmt.Sprintf("protocol = '%s'", quote(string(protocol))),
+		realtimeMileageFramePredicate(),
+	}
+	sqlText := fmt.Sprintf(`SELECT vin, phone, device_id, source_endpoint, LAST(ts), LAST(parsed_json), COUNT(*)
+FROM %s.raw_frames
+WHERE %s
+GROUP BY vin, phone, device_id, source_endpoint`, ident(cfg.TDengineDatabase), strings.Join(where, " AND "))
+	return querySourceRows(ctx, db, cfg, protocol, sqlText, false)
+}
+
+func querySourceRows(ctx context.Context, db *sql.DB, cfg config, protocol envelope.Protocol, sqlText string, includeFirst bool) (map[string][]dailySourceLast, error) {
 	rows, err := db.QueryContext(ctx, sqlText)
 	if err != nil {
 		return nil, err
@@ -458,25 +480,32 @@ GROUP BY vin, phone, device_id, source_endpoint`, ident(cfg.TDengineDatabase), s
 		var phone string
 		var deviceID string
 		var sourceEndpoint string
+		var firstTS time.Time
+		var firstParsedJSON string
 		var ts time.Time
 		var parsedJSON string
-		if err := rows.Scan(&vin, &phone, &deviceID, &sourceEndpoint, &ts, &parsedJSON); err != nil {
+		var rawSampleCount int64
+		if includeFirst {
+			if err := rows.Scan(&vin, &phone, &deviceID, &sourceEndpoint, &firstTS, &firstParsedJSON, &ts, &parsedJSON, &rawSampleCount); err != nil {
 				return nil, err
 			}
-		fields := fieldsForStats(protocol, vin, parsedJSON)
+		} else {
-		env := envelope.FrameEnvelope{
+			if err := rows.Scan(&vin, &phone, &deviceID, &sourceEndpoint, &ts, &parsedJSON, &rawSampleCount); err != nil {
-			Protocol:     protocol,
+				return nil, err
-			VIN:          strings.TrimSpace(vin),
-			EventTimeMS:  time.Now().UnixMilli(),
-			ReceivedAtMS: time.Now().UnixMilli(),
-			Fields:       fields,
-			ParsedFields: fields,
-			ParseStatus:  envelope.ParseOK,
 			}
-		samples, err := stats.SamplesFromEnvelope(env, cfg.Location)
+			firstTS = ts
-		if err != nil || len(samples) == 0 {
+			firstParsedJSON = parsedJSON
+		}
+		latestTotalKM, ok := mileageFromParsed(protocol, vin, parsedJSON, ts, cfg.Location)
+		if !ok {
 			continue
 		}
+		firstTotalKM := latestTotalKM
+		if includeFirst {
+			if parsedFirst, ok := mileageFromParsed(protocol, vin, firstParsedJSON, firstTS, cfg.Location); ok {
+				firstTotalKM = parsedFirst
+			}
+		}
 		sourceKey := normalizedSourceKey(string(protocol), phone, deviceID, sourceEndpoint)
 		if sourceKey == "" {
 			continue
@@ -487,8 +516,11 @@ GROUP BY vin, phone, device_id, source_endpoint`, ident(cfg.TDengineDatabase), s
 			Phone:          strings.TrimSpace(phone),
 			DeviceID:       strings.TrimSpace(deviceID),
 			SourceEndpoint: strings.TrimSpace(sourceEndpoint),
+			FirstTS:        firstTS.In(cfg.Location),
 			TS:             ts,
-			TotalKM:        samples[0].TotalMileageKM,
+			FirstTotalKM:   firstTotalKM,
+			TotalKM:        latestTotalKM,
+			RawSampleCount: rawSampleCount,
 		}
 		key := row.VIN + "|" + row.SourceKey
 		if existing, ok := latestBySource[key]; !ok || row.TS.After(existing.TS) {
@@ -505,6 +537,24 @@ GROUP BY vin, phone, device_id, source_endpoint`, ident(cfg.TDengineDatabase), s
 	return out, nil
 }
 
+func mileageFromParsed(protocol envelope.Protocol, vin string, parsedJSON string, eventTime time.Time, loc *time.Location) (float64, bool) {
+	fields := fieldsForStats(protocol, vin, parsedJSON)
+	env := envelope.FrameEnvelope{
+		Protocol:     protocol,
+		VIN:          strings.TrimSpace(vin),
+		EventTimeMS:  eventTime.UnixMilli(),
+		ReceivedAtMS: eventTime.UnixMilli(),
+		Fields:       fields,
+		ParsedFields: fields,
+		ParseStatus:  envelope.ParseOK,
+	}
+	samples, err := stats.SamplesFromEnvelope(env, loc)
+	if err != nil || len(samples) == 0 {
+		return 0, false
+	}
+	return samples[0].TotalMileageKM, true
+}
+
 func normalizedSourceKey(protocol string, phone string, deviceID string, endpoint string) string {
 	sourceIP := stats.NormalizeSourceIP(endpoint)
 	return stats.SourceKey(envelope.Protocol(protocol), phone, deviceID, sourceIP)

go/vehicle-gateway/cmd/stats-backfill/main_test.go

@@ -67,6 +67,69 @@ func TestDailySourceLastBuildsCandidateKeysBySourceIP(t *testing.T) {
 	}
 }
 
+func TestAggregateFromDailySourceUsesOlderHistoricalBaseline(t *testing.T) {
+	current := dailySourceLast{
+		VIN:            "LMRKH9AC2R1004087",
+		SourceKey:      normalizedSourceKey("YUTONG_MQTT", "", "LMRKH9AC2R1004087", "mqtt://yutong/ytforward/shln/3"),
+		DeviceID:       "LMRKH9AC2R1004087",
+		SourceEndpoint: "mqtt://yutong/ytforward/shln/3",
+		FirstTS:        time.Date(2026, 7, 8, 8, 0, 0, 0, time.FixedZone("Asia/Shanghai", 8*3600)),
+		TS:             time.Date(2026, 7, 8, 17, 0, 0, 0, time.FixedZone("Asia/Shanghai", 8*3600)),
+		FirstTotalKM:   120778,
+		TotalKM:        120788,
+		RawSampleCount: 15,
+	}
+	previous := dailySourceLast{
+		VIN:            "LMRKH9AC2R1004087",
+		SourceKey:      current.SourceKey,
+		DeviceID:       "LMRKH9AC2R1004087",
+		SourceEndpoint: "mqtt://yutong/ytforward/shln/3",
+		TS:             time.Date(2026, 7, 4, 23, 58, 0, 0, time.FixedZone("Asia/Shanghai", 8*3600)),
+		TotalKM:        120672,
+	}
+
+	agg := aggregateFromDailySource("2026-07-08", envelope.ProtocolYutongMQTT, current, previous, true)
+
+	if agg.FirstKM != 120672 || agg.LatestKM != 120788 {
+		t.Fatalf("km range = %v -> %v", agg.FirstKM, agg.LatestKM)
+	}
+	if agg.FirstEventTime != previous.TS || agg.LatestEventTime != current.TS {
+		t.Fatalf("event range = %v -> %v", agg.FirstEventTime, agg.LatestEventTime)
+	}
+	if agg.QualityStatus != stats.QualityOK || agg.QualityReason != "historical_source_baseline" {
+		t.Fatalf("quality = %s/%s", agg.QualityStatus, agg.QualityReason)
+	}
+	if agg.Count != 15 {
+		t.Fatalf("sample count = %d, want 15", agg.Count)
+	}
+}
+
+func TestAggregateFromDailySourceUsesCurrentFirstSampleWithoutHistory(t *testing.T) {
+	current := dailySourceLast{
+		VIN:            "LMRKH9AC2R1004087",
+		SourceKey:      normalizedSourceKey("YUTONG_MQTT", "", "LMRKH9AC2R1004087", "mqtt://yutong/ytforward/shln/3"),
+		DeviceID:       "LMRKH9AC2R1004087",
+		SourceEndpoint: "mqtt://yutong/ytforward/shln/3",
+		FirstTS:        time.Date(2026, 7, 8, 8, 0, 0, 0, time.FixedZone("Asia/Shanghai", 8*3600)),
+		TS:             time.Date(2026, 7, 8, 17, 0, 0, 0, time.FixedZone("Asia/Shanghai", 8*3600)),
+		FirstTotalKM:   120778,
+		TotalKM:        120788,
+		RawSampleCount: 15,
+	}
+
+	agg := aggregateFromDailySource("2026-07-08", envelope.ProtocolYutongMQTT, current, dailySourceLast{}, false)
+
+	if agg.FirstKM != 120778 || agg.LatestKM != 120788 {
+		t.Fatalf("km range = %v -> %v", agg.FirstKM, agg.LatestKM)
+	}
+	if agg.FirstEventTime != current.FirstTS || agg.LatestEventTime != current.TS {
+		t.Fatalf("event range = %v -> %v", agg.FirstEventTime, agg.LatestEventTime)
+	}
+	if agg.QualityStatus != stats.QualityOK || agg.QualityReason != "current_day_first_sample" {
+		t.Fatalf("quality = %s/%s", agg.QualityStatus, agg.QualityReason)
+	}
+}
+
 func TestClearBackfillTargetMileageClearsExactKey(t *testing.T) {
 	db, mock, err := sqlmock.New()
 	if err != nil {
@@ -219,9 +282,9 @@ func TestWriteAggregatesSkipsBlankSourceBeforeClearingTarget(t *testing.T) {
 	}
 }
 
-func TestAddSamplesKeepsScanCandidatesNoPreviousBaseline(t *testing.T) {
+func TestAddSamplesUsesCurrentDayFirstSampleBaseline(t *testing.T) {
 	loc := time.FixedZone("Asia/Shanghai", 8*3600)
-	samples, err := stats.SamplesFromEnvelope(envelope.FrameEnvelope{
+	firstSamples, err := stats.SamplesFromEnvelope(envelope.FrameEnvelope{
 		Protocol:       envelope.ProtocolJT808,
 		VIN:            "LA9GG64L7PBAF4001",
 		Phone:          "13307765812",
@@ -234,18 +297,38 @@ func TestAddSamplesKeepsScanCandidatesNoPreviousBaseline(t *testing.T) {
 	if err != nil {
 		t.Fatalf("SamplesFromEnvelope() error = %v", err)
 	}
+	secondSamples, err := stats.SamplesFromEnvelope(envelope.FrameEnvelope{
+		Protocol:       envelope.ProtocolJT808,
+		VIN:            "LA9GG64L7PBAF4001",
+		Phone:          "13307765812",
+		SourceEndpoint: "115.231.168.135:20215",
+		EventTimeMS:    time.Date(2026, 7, 8, 13, 0, 0, 0, loc).UnixMilli(),
+		Fields: map[string]any{
+			"jt808.location.total_mileage_km": 4129.9,
+		},
+	}, loc)
+	if err != nil {
+		t.Fatalf("SamplesFromEnvelope() error = %v", err)
+	}
 	aggregates := map[string]*metricAgg{}
-	addSamples(aggregates, samples)
+	addSamples(aggregates, firstSamples)
+	addSamples(aggregates, secondSamples)
 	if len(aggregates) != 1 {
 		t.Fatalf("aggregate count = %d, want 1", len(aggregates))
 	}
 	for _, agg := range aggregates {
-		if agg.QualityStatus != stats.QualityNoPreviousBaseline {
+		if agg.QualityStatus != stats.QualityOK {
-			t.Fatalf("quality = %q, want %q", agg.QualityStatus, stats.QualityNoPreviousBaseline)
+			t.Fatalf("quality = %q, want %q", agg.QualityStatus, stats.QualityOK)
 		}
-		if agg.QualityReason != "scan_backfill_missing_previous_source" {
+		if agg.QualityReason != "current_day_first_sample" {
 			t.Fatalf("quality reason = %q", agg.QualityReason)
 		}
+		if agg.FirstKM != 4123.9 || agg.LatestKM != 4129.9 {
+			t.Fatalf("km range = %v -> %v", agg.FirstKM, agg.LatestKM)
+		}
+		if agg.FirstEventTime != time.Date(2026, 7, 8, 12, 0, 0, 0, loc) {
+			t.Fatalf("first event time = %v", agg.FirstEventTime)
+		}
 	}
 }
 

go/vehicle-gateway/internal/stats/daily_metric.go

@@ -182,15 +182,18 @@ func (w *Writer) applyRealtimeBaseline(ctx context.Context, candidate *SourceMil
 		return err
 	}
 	if !found {
-		candidate.QualityStatus = QualityNoPreviousBaseline
+		candidate.QualityStatus = QualityOK
-		candidate.QualityReason = "missing_previous_source"
+		candidate.QualityReason = "current_day_first_sample"
 		return nil
 	}
 	candidate.FirstTotalKM = baseline.LatestTotalKM
 	candidate.FirstEventTime = baseline.LatestEventTime
 	candidate.DailyKM = candidate.LatestTotalKM - baseline.LatestTotalKM
 	candidate.QualityStatus = QualityOK
-	candidate.QualityReason = "same_source_previous_day"
+	candidate.QualityReason = baseline.QualityReason
+	if candidate.QualityReason == "" {
+		candidate.QualityReason = "historical_source_baseline"
+	}
 	if candidate.DailyKM < 0 || candidate.DailyKM > maxSelectedDailyMileageKM {
 		candidate.QualityStatus = QualityInvalidDelta
 		candidate.QualityReason = "outside_daily_range"

go/vehicle-gateway/internal/stats/daily_metric_test.go

@@ -278,7 +278,7 @@ func TestWriterAppendDedupesRealtimeMileagePerSource(t *testing.T) {
 	}
 }
 
-func TestWriterAppendWritesNoPreviousBaselineCandidateAndCleansProjection(t *testing.T) {
+func TestWriterAppendUsesCurrentSampleWhenNoHistoricalBaseline(t *testing.T) {
 	db, mock, err := sqlmock.New()
 	if err != nil {
 		t.Fatalf("sqlmock.New() error = %v", err)
@@ -303,7 +303,7 @@ func TestWriterAppendWritesNoPreviousBaselineCandidateAndCleansProjection(t *tes
 		WithArgs("JT808", "115.231.168.135", "115.231.168.135:20215", sqlmock.AnyArg(), sqlmock.AnyArg()).
 		WillReturnResult(sqlmock.NewResult(0, 1))
 	mock.ExpectQuery(`SELECT latest_total_mileage_km, latest_event_time FROM vehicle_daily_mileage_source`).
-		WithArgs("LA9GG64L7PBAF4001", "2026-07-07", "JT808", "JT808:13307765812@115.231.168.135").
+		WithArgs("LA9GG64L7PBAF4001", "2026-07-08", "JT808", "JT808:13307765812@115.231.168.135").
 		WillReturnRows(sqlmock.NewRows([]string{"latest_total_mileage_km", "latest_event_time"}))
 	mock.ExpectQuery(`SELECT first_total_mileage_km, first_event_time FROM vehicle_daily_mileage_source`).
 		WithArgs("LA9GG64L7PBAF4001", "2026-07-08", "JT808", "JT808:13307765812@115.231.168.135").
@@ -325,8 +325,8 @@ func TestWriterAppendWritesNoPreviousBaselineCandidateAndCleansProjection(t *tes
 			int64(1),
 			eventTime,
 			eventTime,
-			QualityNoPreviousBaseline,
+			QualityOK,
-			"missing_previous_source",
+			"current_day_first_sample",
 		).
 		WillReturnResult(sqlmock.NewResult(0, 1))
 	mock.ExpectExec(`UPDATE vehicle_daily_mileage_source`).
@@ -334,7 +334,7 @@ func TestWriterAppendWritesNoPreviousBaselineCandidateAndCleansProjection(t *tes
 		WillReturnResult(sqlmock.NewResult(0, 0))
 	mock.ExpectExec(`INSERT INTO vehicle_daily_mileage`).
 		WithArgs("LA9GG64L7PBAF4001", "2026-07-08", "JT808", int64(1000)).
-		WillReturnResult(sqlmock.NewResult(0, 0))
+		WillReturnResult(sqlmock.NewResult(0, 1))
 	mock.ExpectExec(`UPDATE vehicle_daily_mileage_source s`).
 		WithArgs(
 			"LA9GG64L7PBAF4001",
@@ -345,7 +345,7 @@ func TestWriterAppendWritesNoPreviousBaselineCandidateAndCleansProjection(t *tes
 			"2026-07-08",
 			"JT808",
 		).
-		WillReturnResult(sqlmock.NewResult(0, 0))
+		WillReturnResult(sqlmock.NewResult(0, 1))
 	mock.ExpectExec(`DELETE FROM vehicle_daily_mileage`).
 		WithArgs(
 			"LA9GG64L7PBAF4001",
@@ -355,7 +355,7 @@ func TestWriterAppendWritesNoPreviousBaselineCandidateAndCleansProjection(t *tes
 			"2026-07-08",
 			"JT808",
 		).
-		WillReturnResult(sqlmock.NewResult(0, 1))
+		WillReturnResult(sqlmock.NewResult(0, 0))
 
 	if err := writer.Append(context.Background(), event); err != nil {
 		t.Fatalf("Append() error = %v", err)
@@ -391,7 +391,7 @@ func TestWriterAppendUsesPreviousSourceBaselineForRealtimeCandidate(t *testing.T
 		WithArgs("JT808", "115.231.168.135", "115.231.168.135:20215", sqlmock.AnyArg(), sqlmock.AnyArg()).
 		WillReturnResult(sqlmock.NewResult(0, 1))
 	mock.ExpectQuery(`SELECT latest_total_mileage_km, latest_event_time FROM vehicle_daily_mileage_source`).
-		WithArgs("LA9GG64L7PBAF4001", "2026-07-07", "JT808", "JT808:13307765812@115.231.168.135").
+		WithArgs("LA9GG64L7PBAF4001", "2026-07-08", "JT808", "JT808:13307765812@115.231.168.135").
 		WillReturnRows(sqlmock.NewRows([]string{"latest_total_mileage_km", "latest_event_time"}).
 			AddRow(4100.8, previousTime))
 	mock.ExpectExec(`INSERT INTO vehicle_daily_mileage_source`).
@@ -412,7 +412,7 @@ func TestWriterAppendUsesPreviousSourceBaselineForRealtimeCandidate(t *testing.T
 			previousTime,
 			currentTime,
 			QualityOK,
-			"same_source_previous_day",
+			"historical_source_baseline",
 		).
 		WillReturnResult(sqlmock.NewResult(0, 1))
 	mock.ExpectExec(`UPDATE vehicle_daily_mileage_source`).
@@ -451,6 +451,92 @@ func TestWriterAppendUsesPreviousSourceBaselineForRealtimeCandidate(t *testing.T
 	}
 }
 
+func TestWriterAppendUsesOlderHistoricalSourceBaseline(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("sqlmock.New() error = %v", err)
+	}
+	defer db.Close()
+
+	loc := time.FixedZone("Asia/Shanghai", 8*3600)
+	writer := NewWriter(db, loc)
+	historicalTime := time.Date(2026, 7, 4, 23, 58, 0, 0, loc)
+	currentTime := time.Date(2026, 7, 8, 13, 20, 0, 0, loc)
+	event := envelope.FrameEnvelope{
+		Protocol:       envelope.ProtocolYutongMQTT,
+		VIN:            "LMRKH9AC2R1004087",
+		DeviceID:       "LMRKH9AC2R1004087",
+		SourceEndpoint: "mqtt://yutong/ytforward/shln/3",
+		EventTimeMS:    currentTime.UnixMilli(),
+		Fields: map[string]any{
+			"yutong_mqtt.data.total_mileage": 120788000,
+		},
+	}
+
+	mock.ExpectExec(`INSERT INTO vehicle_data_source`).
+		WithArgs("YUTONG_MQTT", "mqtt", "mqtt://yutong/ytforward/shln/3", sqlmock.AnyArg(), sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectQuery(`SELECT latest_total_mileage_km, latest_event_time FROM vehicle_daily_mileage_source`).
+		WithArgs("LMRKH9AC2R1004087", "2026-07-08", "YUTONG_MQTT", "YUTONG_MQTT:LMRKH9AC2R1004087@mqtt").
+		WillReturnRows(sqlmock.NewRows([]string{"latest_total_mileage_km", "latest_event_time"}).
+			AddRow(120672.0, historicalTime))
+	mock.ExpectExec(`INSERT INTO vehicle_daily_mileage_source`).
+		WithArgs(
+			"LMRKH9AC2R1004087",
+			"2026-07-08",
+			"YUTONG_MQTT",
+			"YUTONG_MQTT:LMRKH9AC2R1004087@mqtt",
+			"mqtt",
+			"mqtt://yutong/ytforward/shln/3",
+			"",
+			"LMRKH9AC2R1004087",
+			"",
+			float64(120672.0),
+			float64(120788.0),
+			approxFloat64{want: 116.0, tolerance: 0.000001},
+			int64(1),
+			historicalTime,
+			currentTime,
+			QualityOK,
+			"historical_source_baseline",
+		).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectExec(`UPDATE vehicle_daily_mileage_source`).
+		WithArgs("LMRKH9AC2R1004087", "2026-07-08", "YUTONG_MQTT").
+		WillReturnResult(sqlmock.NewResult(0, 0))
+	mock.ExpectExec(`INSERT INTO vehicle_daily_mileage`).
+		WithArgs("LMRKH9AC2R1004087", "2026-07-08", "YUTONG_MQTT", int64(1000)).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectExec(`UPDATE vehicle_daily_mileage_source s`).
+		WithArgs(
+			"LMRKH9AC2R1004087",
+			"2026-07-08",
+			"YUTONG_MQTT",
+			int64(1000),
+			"LMRKH9AC2R1004087",
+			"2026-07-08",
+			"YUTONG_MQTT",
+		).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectExec(`DELETE FROM vehicle_daily_mileage`).
+		WithArgs(
+			"LMRKH9AC2R1004087",
+			"2026-07-08",
+			"YUTONG_MQTT",
+			"LMRKH9AC2R1004087",
+			"2026-07-08",
+			"YUTONG_MQTT",
+		).
+		WillReturnResult(sqlmock.NewResult(0, 0))
+
+	if err := writer.Append(context.Background(), event); err != nil {
+		t.Fatalf("Append() error = %v", err)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatalf("sql expectations: %v", err)
+	}
+}
+
 func TestWriterAppendUsesCurrentOKCandidateWhenPreviousBaselineMissing(t *testing.T) {
 	db, mock, err := sqlmock.New()
 	if err != nil {
@@ -477,7 +563,7 @@ func TestWriterAppendUsesCurrentOKCandidateWhenPreviousBaselineMissing(t *testin
 		WithArgs("JT808", "115.231.168.135", "115.231.168.135:20215", sqlmock.AnyArg(), sqlmock.AnyArg()).
 		WillReturnResult(sqlmock.NewResult(0, 1))
 	mock.ExpectQuery(`SELECT latest_total_mileage_km, latest_event_time FROM vehicle_daily_mileage_source`).
-		WithArgs("LA9GG64L7PBAF4001", "2026-07-07", "JT808", "JT808:13307765812@115.231.168.135").
+		WithArgs("LA9GG64L7PBAF4001", "2026-07-08", "JT808", "JT808:13307765812@115.231.168.135").
 		WillReturnRows(sqlmock.NewRows([]string{"latest_total_mileage_km", "latest_event_time"}))
 	mock.ExpectQuery(`SELECT first_total_mileage_km, first_event_time FROM vehicle_daily_mileage_source`).
 		WithArgs("LA9GG64L7PBAF4001", "2026-07-08", "JT808", "JT808:13307765812@115.231.168.135").
@@ -501,7 +587,7 @@ func TestWriterAppendUsesCurrentOKCandidateWhenPreviousBaselineMissing(t *testin
 			firstTime,
 			currentTime,
 			QualityOK,
-			"same_source_previous_day",
+			"current_day_first_sample",
 		).
 		WillReturnResult(sqlmock.NewResult(0, 1))
 	mock.ExpectExec(`UPDATE vehicle_daily_mileage_source`).

go/vehicle-gateway/internal/stats/source_mileage.go

@@ -273,17 +273,14 @@ WHERE vin = ? AND stat_date = ? AND protocol = ?
 type sourceBaseline struct {
 	LatestTotalKM   float64
 	LatestEventTime time.Time
+	QualityReason   string
 }
 
 func lookupPreviousSourceBaseline(ctx context.Context, query Queryer, vin string, statDate string, protocol envelope.Protocol, sourceKey string) (sourceBaseline, bool, error) {
 	if query == nil || strings.TrimSpace(vin) == "" || strings.TrimSpace(statDate) == "" || strings.TrimSpace(sourceKey) == "" {
 		return sourceBaseline{}, false, nil
 	}
-	previousDate, ok := previousStatDate(statDate)
+	rows, err := query.QueryContext(ctx, previousSourceBaselineSQL, vin, statDate, string(protocol), sourceKey)
-	if !ok {
-		return sourceBaseline{}, false, nil
-	}
-	rows, err := query.QueryContext(ctx, previousSourceBaselineSQL, vin, previousDate, string(protocol), sourceKey)
 	if err != nil {
 		return sourceBaseline{}, false, err
 	}
@@ -305,6 +302,7 @@ func lookupPreviousSourceBaseline(ctx context.Context, query Queryer, vin string
 	return sourceBaseline{
 		LatestTotalKM:   latestTotal.Float64,
 		LatestEventTime: latestEvent.Time,
+		QualityReason:   "historical_source_baseline",
 	}, latestTotal.Valid, nil
 }
 
@@ -334,25 +332,19 @@ func lookupCurrentSourceBaseline(ctx context.Context, query Queryer, vin string,
 	return sourceBaseline{
 		LatestTotalKM:   firstTotal.Float64,
 		LatestEventTime: firstEvent.Time,
+		QualityReason:   "current_day_first_sample",
 	}, firstTotal.Valid, nil
 }
 
-func previousStatDate(statDate string) (string, bool) {
-	day, err := time.Parse("2006-01-02", strings.TrimSpace(statDate))
-	if err != nil {
-		return "", false
-	}
-	return day.AddDate(0, 0, -1).Format("2006-01-02"), true
-}
-
 const previousSourceBaselineSQL = `
 SELECT latest_total_mileage_km, latest_event_time
 FROM vehicle_daily_mileage_source
 WHERE vin = ?
-  AND stat_date = ?
+  AND stat_date < ?
   AND protocol = ?
   AND source_key = ?
-ORDER BY latest_event_time DESC
+  AND quality_status = '` + QualityOK + `'
+ORDER BY stat_date DESC, latest_event_time DESC
 LIMIT 1
 `