refactor(go): simplify daily mileage storage

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

@@ -11,11 +11,6 @@ import (
 	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
 )
 
-const (
-	MetricDailyMileageKM      = "daily_mileage_km"
-	MetricDailyTotalMileageKM = "daily_total_mileage_km"
-)
-
 type Execer interface {
 	ExecContext(context.Context, string, ...any) (sql.Result, error)
 }
@@ -30,8 +25,6 @@ type MetricSample struct {
 	VIN            string
 	Protocol       envelope.Protocol
 	StatDate       string
-	MetricKey      string
-	MetricValue    float64
 	TotalMileageKM float64
 }
 
@@ -46,12 +39,9 @@ func NewWriter(exec Execer, loc *time.Location) *Writer {
 }
 
 func (w *Writer) EnsureSchema(ctx context.Context) error {
-	if _, err := w.exec.ExecContext(ctx, DailyMetricTableSQL); err != nil {
+	if _, err := w.exec.ExecContext(ctx, DailyMileageTableSQL); err != nil {
 		return err
 	}
-	if db, ok := w.exec.(metadataDB); ok {
-		return migrateDailyMetricTable(ctx, db)
-	}
 	return nil
 }
 
@@ -61,13 +51,11 @@ func (w *Writer) Append(ctx context.Context, env envelope.FrameEnvelope) error {
 		return err
 	}
 	for _, sample := range samples {
-		if _, err := w.exec.ExecContext(ctx, upsertDailyMetricSQL,
+		if _, err := w.exec.ExecContext(ctx, upsertDailyMileageSQL,
 			sample.VehicleKey,
 			sample.VIN,
 			sample.StatDate,
 			string(sample.Protocol),
-			sample.MetricKey,
-			sample.MetricValue,
 			sample.TotalMileageKM,
 			sample.TotalMileageKM); err != nil {
 			return err
@@ -100,33 +88,20 @@ func SamplesFromEnvelope(env envelope.FrameEnvelope, loc *time.Location) ([]Metr
 		return nil, errors.New("event or received time is required")
 	}
 	statDate := time.UnixMilli(eventMS).In(loc).Format("2006-01-02")
-	return []MetricSample{
-		{
-			VehicleKey:     vehicleKey,
-			VIN:            vin,
-			Protocol:       env.Protocol,
-			StatDate:       statDate,
-			MetricKey:      MetricDailyMileageKM,
-			MetricValue:    0,
-			TotalMileageKM: totalMileage,
-		},
-		{
-			VehicleKey:     vehicleKey,
-			VIN:            vin,
-			Protocol:       env.Protocol,
-			StatDate:       statDate,
-			MetricKey:      MetricDailyTotalMileageKM,
-			MetricValue:    totalMileage,
-			TotalMileageKM: totalMileage,
-		},
-	}, nil
+	return []MetricSample{{
+		VehicleKey:     vehicleKey,
+		VIN:            vin,
+		Protocol:       env.Protocol,
+		StatDate:       statDate,
+		TotalMileageKM: totalMileage,
+	}}, nil
 }
 
-const upsertDailyMetricSQL = `
-INSERT INTO vehicle_daily_metric
-  (vehicle_key, vin, stat_date, protocol, metric_key, metric_value, metric_unit,
-   first_total_mileage_km, latest_total_mileage_km, sample_count, calculation_method)
-VALUES (?, ?, ?, ?, ?, ?, 'km', ?, ?, 1, 'TOTAL_MILEAGE_DIFF')
+const upsertDailyMileageSQL = `
+INSERT INTO vehicle_daily_mileage
+  (vehicle_key, vin, stat_date, protocol, daily_mileage_km,
+   first_total_mileage_km, latest_total_mileage_km, sample_count)
+VALUES (?, ?, ?, ?, 0, ?, ?, 1)
 ON DUPLICATE KEY UPDATE
   vin = IF(VALUES(vin) <> '', VALUES(vin), vin),
   first_total_mileage_km = CASE
@@ -139,112 +114,22 @@ ON DUPLICATE KEY UPDATE
       THEN VALUES(latest_total_mileage_km)
     ELSE GREATEST(latest_total_mileage_km, VALUES(latest_total_mileage_km))
   END,
-  metric_value = CASE
-    WHEN metric_key = 'daily_mileage_km'
-      THEN GREATEST(
-             CASE
-               WHEN latest_total_mileage_km IS NULL OR latest_total_mileage_km <= 0
-                 THEN VALUES(latest_total_mileage_km)
-               ELSE latest_total_mileage_km
-             END,
-             VALUES(latest_total_mileage_km)
-           )
-           - CASE
-               WHEN first_total_mileage_km IS NULL OR first_total_mileage_km <= 0
-                 THEN VALUES(first_total_mileage_km)
-               ELSE LEAST(first_total_mileage_km, VALUES(first_total_mileage_km))
-             END
-    WHEN metric_key = 'daily_total_mileage_km'
-      THEN GREATEST(
-             CASE
-               WHEN latest_total_mileage_km IS NULL OR latest_total_mileage_km <= 0
-                 THEN VALUES(latest_total_mileage_km)
-               ELSE latest_total_mileage_km
-             END,
-             VALUES(latest_total_mileage_km)
-           )
-    ELSE VALUES(metric_value)
+  daily_mileage_km = GREATEST(
+    CASE
+      WHEN latest_total_mileage_km IS NULL OR latest_total_mileage_km <= 0
+        THEN VALUES(latest_total_mileage_km)
+      ELSE latest_total_mileage_km
+    END,
+    VALUES(latest_total_mileage_km)
+  ) - CASE
+    WHEN first_total_mileage_km IS NULL OR first_total_mileage_km <= 0
+      THEN VALUES(first_total_mileage_km)
+    ELSE LEAST(first_total_mileage_km, VALUES(first_total_mileage_km))
   END,
   sample_count = sample_count + 1,
   updated_at = CURRENT_TIMESTAMP
 `
 
-type metadataDB interface {
-	Execer
-	QueryRowContext(context.Context, string, ...any) *sql.Row
-}
-
-func migrateDailyMetricTable(ctx context.Context, db metadataDB) error {
-	columnExists, err := informationSchemaExists(ctx, db, `
-SELECT COUNT(*)
-FROM information_schema.columns
-WHERE table_schema = DATABASE()
-  AND table_name = 'vehicle_daily_metric'
-  AND column_name = 'vehicle_key'`)
-	if err != nil {
-		return err
-	}
-	if !columnExists {
-		if _, err := db.ExecContext(ctx, `ALTER TABLE vehicle_daily_metric ADD COLUMN vehicle_key VARCHAR(96) NOT NULL DEFAULT '' AFTER id`); err != nil {
-			return err
-		}
-	}
-	if _, err := db.ExecContext(ctx, `UPDATE vehicle_daily_metric SET vehicle_key = vin WHERE vehicle_key = ''`); err != nil {
-		return err
-	}
-	vehicleIndexExists, err := informationSchemaExists(ctx, db, `
-SELECT COUNT(*)
-FROM information_schema.statistics
-WHERE table_schema = DATABASE()
-  AND table_name = 'vehicle_daily_metric'
-  AND index_name = 'uk_daily_metric_vehicle'`)
-	if err != nil {
-		return err
-	}
-	if !vehicleIndexExists {
-		if _, err := db.ExecContext(ctx, `ALTER TABLE vehicle_daily_metric ADD UNIQUE KEY uk_daily_metric_vehicle (vehicle_key, stat_date, protocol, metric_key)`); err != nil {
-			return err
-		}
-	}
-	oldIndexExists, err := informationSchemaExists(ctx, db, `
-SELECT COUNT(*)
-FROM information_schema.statistics
-WHERE table_schema = DATABASE()
-  AND table_name = 'vehicle_daily_metric'
-  AND index_name = 'uk_daily_metric'`)
-	if err != nil {
-		return err
-	}
-	if oldIndexExists {
-		if _, err := db.ExecContext(ctx, `ALTER TABLE vehicle_daily_metric DROP INDEX uk_daily_metric`); err != nil {
-			return err
-		}
-	}
-	vinIndexExists, err := informationSchemaExists(ctx, db, `
-SELECT COUNT(*)
-FROM information_schema.statistics
-WHERE table_schema = DATABASE()
-  AND table_name = 'vehicle_daily_metric'
-  AND index_name = 'idx_vin'`)
-	if err != nil {
-		return err
-	}
-	if !vinIndexExists {
-		if _, err := db.ExecContext(ctx, `ALTER TABLE vehicle_daily_metric ADD KEY idx_vin (vin)`); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
-func informationSchemaExists(ctx context.Context, db metadataDB, query string) (bool, error) {
-	var count int
-	if err := db.QueryRowContext(ctx, query).Scan(&count); err != nil {
-		return false, err
-	}
-	return count > 0, nil
-}
-
 func floatField(env envelope.FrameEnvelope, key string) (float64, bool) {
 	if env.Fields == nil {
 		return 0, false

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

@@ -10,7 +10,7 @@ import (
 	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
 )
 
-func TestSamplesFromEnvelopeDerivesDailyMileageAndTotal(t *testing.T) {
+func TestSamplesFromEnvelopeDerivesDailyMileageSample(t *testing.T) {
 	loc := time.FixedZone("Asia/Shanghai", 8*3600)
 	env := envelope.FrameEnvelope{
 		Protocol:    envelope.ProtocolJT808,
@@ -25,17 +25,14 @@ func TestSamplesFromEnvelopeDerivesDailyMileageAndTotal(t *testing.T) {
 	if err != nil {
 		t.Fatalf("SamplesFromEnvelope() error = %v", err)
 	}
-	if len(samples) != 2 {
+	if len(samples) != 1 {
 		t.Fatalf("sample count = %d", len(samples))
 	}
-	if samples[0].MetricKey != MetricDailyMileageKM || samples[0].MetricValue != 0 {
-		t.Fatalf("unexpected daily mileage sample: %#v", samples[0])
-	}
 	if samples[0].VehicleKey != "LNBVIN00000000001" {
 		t.Fatalf("vehicle key = %q", samples[0].VehicleKey)
 	}
-	if samples[1].MetricKey != MetricDailyTotalMileageKM || samples[1].MetricValue != 10241.2 {
-		t.Fatalf("unexpected daily total sample: %#v", samples[1])
+	if samples[0].TotalMileageKM != 10241.2 {
+		t.Fatalf("total mileage = %v", samples[0].TotalMileageKM)
 	}
 	if samples[0].StatDate != "2026-07-01" {
 		t.Fatalf("stat date = %q", samples[0].StatDate)
@@ -55,7 +52,7 @@ func TestSamplesFromEnvelopeUsesVehicleKeyWhenVINIsMissing(t *testing.T) {
 	if err != nil {
 		t.Fatalf("SamplesFromEnvelope() error = %v", err)
 	}
-	if len(samples) != 2 {
+	if len(samples) != 1 {
 		t.Fatalf("sample count = %d", len(samples))
 	}
 	if samples[0].VehicleKey != "JT808:13307811254" {
@@ -110,7 +107,7 @@ func TestSamplesFromEnvelopeSkipsNonPositiveMileage(t *testing.T) {
 	}
 }
 
-func TestWriterEnsuresSchemaAndUpsertsTwoMetrics(t *testing.T) {
+func TestWriterEnsuresSchemaAndUpsertsDailyMileage(t *testing.T) {
 	exec := &recordingExec{}
 	writer := NewWriter(exec, time.FixedZone("Asia/Shanghai", 8*3600))
 	if err := writer.EnsureSchema(context.Background()); err != nil {
@@ -127,18 +124,21 @@ func TestWriterEnsuresSchemaAndUpsertsTwoMetrics(t *testing.T) {
 		t.Fatalf("Append() error = %v", err)
 	}
 
-	if !strings.Contains(exec.calls[0].query, "CREATE TABLE IF NOT EXISTS vehicle_daily_metric") {
+	if !strings.Contains(exec.calls[0].query, "CREATE TABLE IF NOT EXISTS vehicle_daily_mileage") {
 		t.Fatalf("unexpected schema sql: %s", exec.calls[0].query)
 	}
 	if !strings.Contains(exec.calls[0].query, "vehicle_key") {
 		t.Fatalf("schema should include vehicle_key: %s", exec.calls[0].query)
 	}
-	if len(exec.calls) != 3 {
+	if len(exec.calls) != 2 {
 		t.Fatalf("exec calls = %d", len(exec.calls))
 	}
 	if !strings.Contains(exec.calls[1].query, "ON DUPLICATE KEY UPDATE") {
 		t.Fatalf("unexpected upsert sql: %s", exec.calls[1].query)
 	}
+	if strings.Contains(exec.calls[1].query, "metric_key") || strings.Contains(exec.calls[1].query, "metric_unit") {
+		t.Fatalf("daily mileage upsert should not use generic metric columns: %s", exec.calls[1].query)
+	}
 	if !strings.Contains(exec.calls[1].query, "first_total_mileage_km <= 0") {
 		t.Fatalf("upsert should ignore legacy zero first mileage: %s", exec.calls[1].query)
 	}

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

@@ -20,7 +20,6 @@ type MetricQuery struct {
 	VehicleKey string
 	VIN        string
 	Protocol   string
-	MetricKey  string
 	DateFrom   string
 	DateTo     string
 	Limit      int
@@ -32,13 +31,10 @@ type MetricRow struct {
 	VIN                  string   `json:"vin"`
 	StatDate             string   `json:"stat_date"`
 	Protocol             string   `json:"protocol"`
-	MetricKey            string   `json:"metric_key"`
-	MetricValue          float64  `json:"metric_value"`
-	MetricUnit           string   `json:"metric_unit"`
+	DailyMileageKM       float64  `json:"daily_mileage_km"`
 	FirstTotalMileageKM  *float64 `json:"first_total_mileage_km,omitempty"`
 	LatestTotalMileageKM *float64 `json:"latest_total_mileage_km,omitempty"`
 	SampleCount          int64    `json:"sample_count"`
-	CalculationMethod    string   `json:"calculation_method"`
 	CreatedAt            string   `json:"created_at"`
 	UpdatedAt            string   `json:"updated_at"`
 }
@@ -76,13 +72,10 @@ func (r *MetricRepository) Query(ctx context.Context, query MetricQuery) ([]Metr
 			&row.VIN,
 			&statDate,
 			&row.Protocol,
-			&row.MetricKey,
-			&row.MetricValue,
-			&row.MetricUnit,
+			&row.DailyMileageKM,
 			&first,
 			&latest,
 			&row.SampleCount,
-			&row.CalculationMethod,
 			&createdAt,
 			&updatedAt,
 		); err != nil {
@@ -124,7 +117,6 @@ func normalizeMetricQuery(query MetricQuery) MetricQuery {
 	query.VehicleKey = strings.TrimSpace(query.VehicleKey)
 	query.VIN = strings.TrimSpace(query.VIN)
 	query.Protocol = strings.ToUpper(strings.TrimSpace(query.Protocol))
-	query.MetricKey = strings.TrimSpace(query.MetricKey)
 	query.DateFrom = strings.TrimSpace(query.DateFrom)
 	query.DateTo = strings.TrimSpace(query.DateTo)
 	if query.Limit <= 0 {
@@ -135,18 +127,18 @@ func normalizeMetricQuery(query MetricQuery) MetricQuery {
 
 func buildMetricSQL(query MetricQuery) (string, []any) {
 	where, args := buildMetricWhere(query)
-	sqlText := `SELECT vehicle_key, vin, stat_date, protocol, metric_key, metric_value, metric_unit, first_total_mileage_km, latest_total_mileage_km, sample_count, calculation_method, created_at, updated_at FROM vehicle_daily_metric`
+	sqlText := `SELECT vehicle_key, vin, stat_date, protocol, daily_mileage_km, first_total_mileage_km, latest_total_mileage_km, sample_count, created_at, updated_at FROM vehicle_daily_mileage`
 	if len(where) > 0 {
 		sqlText += " WHERE " + strings.Join(where, " AND ")
 	}
-	sqlText += " ORDER BY stat_date DESC, vehicle_key ASC, protocol ASC, metric_key ASC LIMIT ? OFFSET ?"
+	sqlText += " ORDER BY stat_date DESC, vehicle_key ASC, protocol ASC LIMIT ? OFFSET ?"
 	args = append(args, query.Limit, query.Offset)
 	return sqlText, args
 }
 
 func buildMetricCountSQL(query MetricQuery) (string, []any) {
 	where, args := buildMetricWhere(query)
-	sqlText := `SELECT COUNT(*) FROM vehicle_daily_metric`
+	sqlText := `SELECT COUNT(*) FROM vehicle_daily_mileage`
 	if len(where) > 0 {
 		sqlText += " WHERE " + strings.Join(where, " AND ")
 	}
@@ -169,9 +161,6 @@ func buildMetricWhere(query MetricQuery) ([]string, []any) {
 	if query.Protocol != "" {
 		add("protocol = ?", query.Protocol)
 	}
-	if query.MetricKey != "" {
-		add("metric_key = ?", query.MetricKey)
-	}
 	if query.DateFrom != "" {
 		add("stat_date >= ?", query.DateFrom)
 	}
@@ -239,7 +228,6 @@ func parseMetricQuery(r *http.Request) (MetricQuery, error) {
 		VehicleKey: values.Get("vehicleKey"),
 		VIN:        values.Get("vin"),
 		Protocol:   values.Get("protocol"),
-		MetricKey:  values.Get("metricKey"),
 		DateFrom:   values.Get("dateFrom"),
 		DateTo:     values.Get("dateTo"),
 		Limit:      limit,

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

@@ -18,15 +18,15 @@ func TestMetricRepositoryQueriesDailyMetricsWithFilters(t *testing.T) {
 		t.Fatalf("sqlmock.New() error = %v", err)
 	}
 	defer db.Close()
-	mock.ExpectQuery("SELECT vehicle_key, vin, stat_date, protocol, metric_key, metric_value, metric_unit, first_total_mileage_km, latest_total_mileage_km, sample_count, calculation_method, created_at, updated_at FROM vehicle_daily_metric").
+	mock.ExpectQuery("SELECT vehicle_key, vin, stat_date, protocol, daily_mileage_km, first_total_mileage_km, latest_total_mileage_km, sample_count, created_at, updated_at FROM vehicle_daily_mileage").
 		WithArgs("LKLG7C4E3NA774736", "JT808", "2026-07-01", "2026-07-01", 20, 0).
 		WillReturnRows(sqlmock.NewRows([]string{
-			"vehicle_key", "vin", "stat_date", "protocol", "metric_key", "metric_value", "metric_unit",
-			"first_total_mileage_km", "latest_total_mileage_km", "sample_count", "calculation_method",
+			"vehicle_key", "vin", "stat_date", "protocol", "daily_mileage_km",
+			"first_total_mileage_km", "latest_total_mileage_km", "sample_count",
 			"created_at", "updated_at",
 		}).AddRow(
-			"LKLG7C4E3NA774736", "LKLG7C4E3NA774736", time.Date(2026, 7, 1, 0, 0, 0, 0, time.FixedZone("Asia/Shanghai", 8*3600)), "JT808", MetricDailyTotalMileageKM, 12345.6, "km",
-			12345.6, 12345.6, 13, "TOTAL_MILEAGE_DIFF", time.Date(2026, 7, 1, 22, 49, 11, 0, time.FixedZone("Asia/Shanghai", 8*3600)), time.Date(2026, 7, 1, 23, 9, 36, 0, time.FixedZone("Asia/Shanghai", 8*3600)),
+			"LKLG7C4E3NA774736", "LKLG7C4E3NA774736", time.Date(2026, 7, 1, 0, 0, 0, 0, time.FixedZone("Asia/Shanghai", 8*3600)), "JT808", 12.3,
+			12345.6, 12357.9, 13, time.Date(2026, 7, 1, 22, 49, 11, 0, time.FixedZone("Asia/Shanghai", 8*3600)), time.Date(2026, 7, 1, 23, 9, 36, 0, time.FixedZone("Asia/Shanghai", 8*3600)),
 		))
 
 	repository := NewMetricRepository(db)
@@ -43,7 +43,7 @@ func TestMetricRepositoryQueriesDailyMetricsWithFilters(t *testing.T) {
 	if len(rows) != 1 {
 		t.Fatalf("row count = %d", len(rows))
 	}
-	if rows[0].MetricKey != MetricDailyTotalMileageKM || rows[0].MetricValue != 12345.6 {
+	if rows[0].DailyMileageKM != 12.3 {
 		t.Fatalf("unexpected row: %#v", rows[0])
 	}
 	if rows[0].VehicleKey != "LKLG7C4E3NA774736" {
@@ -63,18 +63,18 @@ func TestMetricHandlerReturnsDailyMetrics(t *testing.T) {
 		t.Fatalf("sqlmock.New() error = %v", err)
 	}
 	defer db.Close()
-	mock.ExpectQuery("SELECT COUNT\\(\\*\\) FROM vehicle_daily_metric").
+	mock.ExpectQuery("SELECT COUNT\\(\\*\\) FROM vehicle_daily_mileage").
 		WithArgs("LB9A32A21R0LS1707", "GB32960", "2020-07-01", "2020-07-01").
 		WillReturnRows(sqlmock.NewRows([]string{"total"}).AddRow(42))
-	mock.ExpectQuery("SELECT vehicle_key, vin, stat_date, protocol, metric_key, metric_value, metric_unit, first_total_mileage_km, latest_total_mileage_km, sample_count, calculation_method, created_at, updated_at FROM vehicle_daily_metric").
+	mock.ExpectQuery("SELECT vehicle_key, vin, stat_date, protocol, daily_mileage_km, first_total_mileage_km, latest_total_mileage_km, sample_count, created_at, updated_at FROM vehicle_daily_mileage").
 		WithArgs("LB9A32A21R0LS1707", "GB32960", "2020-07-01", "2020-07-01", 50, 0).
 		WillReturnRows(sqlmock.NewRows([]string{
-			"vehicle_key", "vin", "stat_date", "protocol", "metric_key", "metric_value", "metric_unit",
-			"first_total_mileage_km", "latest_total_mileage_km", "sample_count", "calculation_method",
+			"vehicle_key", "vin", "stat_date", "protocol", "daily_mileage_km",
+			"first_total_mileage_km", "latest_total_mileage_km", "sample_count",
 			"created_at", "updated_at",
 		}).AddRow(
-			"LB9A32A21R0LS1707", "LB9A32A21R0LS1707", "2020-07-01", "GB32960", MetricDailyMileageKM, 0.0, "km",
-			53490.9, 53490.9, 3, "TOTAL_MILEAGE_DIFF", "2026-07-01 22:07:58", "2026-07-01 22:28:25",
+			"LB9A32A21R0LS1707", "LB9A32A21R0LS1707", "2020-07-01", "GB32960", 0.0,
+			53490.9, 53490.9, 3, "2026-07-01 22:07:58", "2026-07-01 22:28:25",
 		))
 
 	handler := NewMetricHandler(NewMetricRepository(db))
@@ -87,7 +87,7 @@ func TestMetricHandlerReturnsDailyMetrics(t *testing.T) {
 		t.Fatalf("status = %d body=%s", response.Code, response.Body.String())
 	}
 	body := response.Body.String()
-	for _, want := range []string{`"vin":"LB9A32A21R0LS1707"`, `"metric_key":"daily_mileage_km"`, `"total":42`} {
+	for _, want := range []string{`"vin":"LB9A32A21R0LS1707"`, `"daily_mileage_km":0`, `"total":42`} {
 		if !strings.Contains(body, want) {
 			t.Fatalf("response missing %s: %s", want, body)
 		}
@@ -103,18 +103,18 @@ func TestMetricHandlerFiltersByVehicleKey(t *testing.T) {
 		t.Fatalf("sqlmock.New() error = %v", err)
 	}
 	defer db.Close()
-	mock.ExpectQuery("SELECT COUNT\\(\\*\\) FROM vehicle_daily_metric").
+	mock.ExpectQuery("SELECT COUNT\\(\\*\\) FROM vehicle_daily_mileage").
 		WithArgs("JT808:013307811254", "JT808").
 		WillReturnRows(sqlmock.NewRows([]string{"total"}).AddRow(12))
-	mock.ExpectQuery("SELECT vehicle_key, vin, stat_date, protocol, metric_key, metric_value, metric_unit, first_total_mileage_km, latest_total_mileage_km, sample_count, calculation_method, created_at, updated_at FROM vehicle_daily_metric").
+	mock.ExpectQuery("SELECT vehicle_key, vin, stat_date, protocol, daily_mileage_km, first_total_mileage_km, latest_total_mileage_km, sample_count, created_at, updated_at FROM vehicle_daily_mileage").
 		WithArgs("JT808:013307811254", "JT808", 50, 0).
 		WillReturnRows(sqlmock.NewRows([]string{
-			"vehicle_key", "vin", "stat_date", "protocol", "metric_key", "metric_value", "metric_unit",
-			"first_total_mileage_km", "latest_total_mileage_km", "sample_count", "calculation_method",
+			"vehicle_key", "vin", "stat_date", "protocol", "daily_mileage_km",
+			"first_total_mileage_km", "latest_total_mileage_km", "sample_count",
 			"created_at", "updated_at",
 		}).AddRow(
-			"JT808:013307811254", "", "2026-07-02", "JT808", MetricDailyTotalMileageKM, 10985.7, "km",
-			10985.7, 10985.7, 1, "TOTAL_MILEAGE_DIFF", "2026-07-02 00:03:00", "2026-07-02 00:03:00",
+			"JT808:013307811254", "", "2026-07-02", "JT808", 0.0,
+			10985.7, 10985.7, 1, "2026-07-02 00:03:00", "2026-07-02 00:03:00",
 		))
 
 	handler := NewMetricHandler(NewMetricRepository(db))
@@ -127,7 +127,7 @@ func TestMetricHandlerFiltersByVehicleKey(t *testing.T) {
 		t.Fatalf("status = %d body=%s", response.Code, response.Body.String())
 	}
 	body := response.Body.String()
-	for _, want := range []string{`"vehicle_key":"JT808:013307811254"`, `"vin":""`, `"metric_value":10985.7`} {
+	for _, want := range []string{`"vehicle_key":"JT808:013307811254"`, `"vin":""`, `"daily_mileage_km":0`} {
 		if !strings.Contains(body, want) {
 			t.Fatalf("response missing %s: %s", want, body)
 		}
@@ -143,14 +143,14 @@ func TestMetricHandlerReturnsEmptyItemsArrayWhenNoRows(t *testing.T) {
 		t.Fatalf("sqlmock.New() error = %v", err)
 	}
 	defer db.Close()
-	mock.ExpectQuery("SELECT COUNT\\(\\*\\) FROM vehicle_daily_metric").
+	mock.ExpectQuery("SELECT COUNT\\(\\*\\) FROM vehicle_daily_mileage").
 		WithArgs("YUTONG_MQTT").
 		WillReturnRows(sqlmock.NewRows([]string{"total"}).AddRow(0))
-	mock.ExpectQuery("SELECT vehicle_key, vin, stat_date, protocol, metric_key, metric_value, metric_unit, first_total_mileage_km, latest_total_mileage_km, sample_count, calculation_method, created_at, updated_at FROM vehicle_daily_metric").
+	mock.ExpectQuery("SELECT vehicle_key, vin, stat_date, protocol, daily_mileage_km, first_total_mileage_km, latest_total_mileage_km, sample_count, created_at, updated_at FROM vehicle_daily_mileage").
 		WithArgs("YUTONG_MQTT", 50, 0).
 		WillReturnRows(sqlmock.NewRows([]string{
-			"vehicle_key", "vin", "stat_date", "protocol", "metric_key", "metric_value", "metric_unit",
-			"first_total_mileage_km", "latest_total_mileage_km", "sample_count", "calculation_method",
+			"vehicle_key", "vin", "stat_date", "protocol", "daily_mileage_km",
+			"first_total_mileage_km", "latest_total_mileage_km", "sample_count",
 			"created_at", "updated_at",
 		}))
 

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

@@ -1,22 +1,19 @@
 package stats
 
-const DailyMetricTableSQL = `CREATE TABLE IF NOT EXISTS vehicle_daily_metric (
+const DailyMileageTableSQL = `CREATE TABLE IF NOT EXISTS vehicle_daily_mileage (
   id BIGINT PRIMARY KEY AUTO_INCREMENT,
   vehicle_key VARCHAR(96) NOT NULL,
   vin VARCHAR(32) NOT NULL DEFAULT '',
   stat_date DATE NOT NULL,
   protocol VARCHAR(32) NOT NULL,
-  metric_key VARCHAR(64) NOT NULL,
-  metric_value DECIMAL(18,3) NOT NULL,
-  metric_unit VARCHAR(16) NOT NULL,
+  daily_mileage_km DECIMAL(18,3) NOT NULL DEFAULT 0,
   first_total_mileage_km DECIMAL(18,3) NULL,
   latest_total_mileage_km DECIMAL(18,3) NULL,
   sample_count BIGINT NOT NULL DEFAULT 0,
-  calculation_method VARCHAR(64) NOT NULL,
   created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
   updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
-  UNIQUE KEY uk_daily_metric_vehicle (vehicle_key, stat_date, protocol, metric_key),
+  UNIQUE KEY uk_daily_mileage_vehicle (vehicle_key, stat_date, protocol),
   KEY idx_vin (vin),
   KEY idx_stat_date (stat_date),
-  KEY idx_protocol_metric (protocol, metric_key)
+  KEY idx_protocol_date (protocol, stat_date)
 )`