refactor(go): simplify daily mileage table key

docs/architecture/production-data-plane-inventory.md

@@ -69,6 +69,8 @@ NATS 部署在 Kafka ECS 内网 `172.17.111.56:4222`。
 | `vehicle_realtime_location` | `protocol`、`vin`、`plate`、经纬度、速度、总里程、SOC、事件时间 | Realtime API/projector | 每协议每 VIN 最新位置业务缓存 |
 | `vehicle_daily_mileage` | `vin`、`stat_date`、`protocol`、`daily_mileage_km`、首末总里程、样本数 | Stat writer | 基于总里程差值的每日里程；无 VIN 数据不进入正式统计表 |
 
+日里程表使用 `(vin, stat_date, protocol)` 作为业务主键，不保留自增 `id` 和 `created_at`；首末总里程和样本数保留用于解释差值计算。
+
 两张实时当前态表均使用 `(protocol, vin)` 作为业务主键，不保留自增 `id` 和 `created_at`；最新更新时间使用 `updated_at`。
 
 不应重新出现：

docs/architecture/storage-minimal-contract.md

@@ -23,7 +23,7 @@
 | TDengine | `vehicle_locations` | 时间、VIN/协议标签、经纬度、速度、方向、SOC、总里程等位置核心字段 | 完整协议 JSON、注册鉴权信息、phone/device_id/vehicle_key 兜底标识 |
 | MySQL | `vehicle_realtime_snapshot` | 每个协议+VIN 的最新事件时间、接收时间、车牌、事件 ID | phone、device、source endpoint、完整 JSON |
 | MySQL | `vehicle_realtime_location` | 每个协议+VIN 的最新位置核心字段 | raw、parsed JSON、消息头内部字段 |
-| MySQL | `vehicle_daily_mileage` | 日期、VIN、协议、日里程、首末总里程、样本数 | 临时 vehicle key、泛化 metric key/value、每帧细节、位置点列表 |
+| MySQL | `vehicle_daily_mileage` | 日期、VIN、协议、日里程、首末总里程、样本数 | 临时 vehicle key、泛化 metric key/value、自增 id、created_at、每帧细节、位置点列表 |
 | MySQL | `vehicle_identity_binding` | 人工维护或导入的 VIN、车牌、phone、device_id 映射 | 注册历史、协议状态 |
 | MySQL | `jt808_registration` | JT808 phone 主键下的注册、鉴权、VIN 匹配状态、来源端点 | GB32960/MQTT 注册信息、位置历史 |
 | Redis | `vehicle:realtime-raw:{protocol}:{vin}` | 每协议最新完整 parsed 状态 | 历史数据、统计结果 |
@@ -43,6 +43,7 @@
 3. `vehicle_daily_mileage` 不再接收临时 `vehicle_key`。
    - 原因：日统计是正式业务指标，应只统计已经定位到 VIN 的车辆。
    - 无 VIN 的 JT808 等数据保留在 raw/Redis/session 中用于排查和待绑定，不进入正式车辆指标。
+   - 状态：schema 使用 `PRIMARY KEY (vin, stat_date, protocol)`，不保留自增 `id` 和 `created_at`；首末总里程和样本数保留为日里程计算状态。
    - 生产：RDS 已在上线前删除泛化 `vehicle_daily_metric`，改为专用 `vehicle_daily_mileage`。
 
 4. `vehicle_locations` 不再接收临时身份兜底字段。

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

@@ -121,8 +121,13 @@ func TestWriterEnsuresSchemaAndUpsertsDailyMileage(t *testing.T) {
 	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") {
+	for _, column := range []string{"vehicle_key", "id BIGINT", "AUTO_INCREMENT", "created_at"} {
-		t.Fatalf("schema should not include vehicle_key: %s", exec.calls[0].query)
+		if strings.Contains(exec.calls[0].query, column) {
+			t.Fatalf("schema should not include %s: %s", column, exec.calls[0].query)
+		}
+	}
+	if !strings.Contains(exec.calls[0].query, "PRIMARY KEY (vin, stat_date, protocol)") {
+		t.Fatalf("daily mileage table should key by vin/stat_date/protocol: %s", exec.calls[0].query)
 	}
 	if len(exec.calls) != 2 {
 		t.Fatalf("exec calls = %d", len(exec.calls))

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

@@ -33,7 +33,6 @@ type MetricRow struct {
 	FirstTotalMileageKM  *float64 `json:"first_total_mileage_km,omitempty"`
 	LatestTotalMileageKM *float64 `json:"latest_total_mileage_km,omitempty"`
 	SampleCount          int64    `json:"sample_count"`
-	CreatedAt            string   `json:"created_at"`
 	UpdatedAt            string   `json:"updated_at"`
 }
 
@@ -61,7 +60,6 @@ func (r *MetricRepository) Query(ctx context.Context, query MetricQuery) ([]Metr
 	for rows.Next() {
 		var row MetricRow
 		var statDate scanDate
-		var createdAt scanDateTime
 		var updatedAt scanDateTime
 		var first sql.NullFloat64
 		var latest sql.NullFloat64
@@ -73,13 +71,11 @@ func (r *MetricRepository) Query(ctx context.Context, query MetricQuery) ([]Metr
 			&first,
 			&latest,
 			&row.SampleCount,
-			&createdAt,
 			&updatedAt,
 		); err != nil {
 			return nil, err
 		}
 		row.StatDate = statDate.String
-		row.CreatedAt = createdAt.String
 		row.UpdatedAt = updatedAt.String
 		if first.Valid {
 			row.FirstTotalMileageKM = &first.Float64
@@ -123,7 +119,7 @@ func normalizeMetricQuery(query MetricQuery) MetricQuery {
 
 func buildMetricSQL(query MetricQuery) (string, []any) {
 	where, args := buildMetricWhere(query)
-	sqlText := `SELECT 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`
+	sqlText := `SELECT vin, stat_date, protocol, daily_mileage_km, first_total_mileage_km, latest_total_mileage_km, sample_count, updated_at FROM vehicle_daily_mileage`
 	if len(where) > 0 {
 		sqlText += " WHERE " + strings.Join(where, " AND ")
 	}

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 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").
+	mock.ExpectQuery("SELECT vin, stat_date, protocol, daily_mileage_km, first_total_mileage_km, latest_total_mileage_km, sample_count, updated_at FROM vehicle_daily_mileage").
 		WithArgs("LKLG7C4E3NA774736", "JT808", "2026-07-01", "2026-07-01", 20, 0).
 		WillReturnRows(sqlmock.NewRows([]string{
 			"vin", "stat_date", "protocol", "daily_mileage_km",
 			"first_total_mileage_km", "latest_total_mileage_km", "sample_count",
-			"created_at", "updated_at",
+			"updated_at",
 		}).AddRow(
 			"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)),
+			12345.6, 12357.9, 13, time.Date(2026, 7, 1, 23, 9, 36, 0, time.FixedZone("Asia/Shanghai", 8*3600)),
 		))
 
 	repository := NewMetricRepository(db)
@@ -63,15 +63,15 @@ func TestMetricHandlerReturnsDailyMetrics(t *testing.T) {
 	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 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").
+	mock.ExpectQuery("SELECT vin, stat_date, protocol, daily_mileage_km, first_total_mileage_km, latest_total_mileage_km, sample_count, updated_at FROM vehicle_daily_mileage").
 		WithArgs("LB9A32A21R0LS1707", "GB32960", "2020-07-01", "2020-07-01", 50, 0).
 		WillReturnRows(sqlmock.NewRows([]string{
 			"vin", "stat_date", "protocol", "daily_mileage_km",
 			"first_total_mileage_km", "latest_total_mileage_km", "sample_count",
-			"created_at", "updated_at",
+			"updated_at",
 		}).AddRow(
 			"LB9A32A21R0LS1707", "2020-07-01", "GB32960", 0.0,
-			53490.9, 53490.9, 3, "2026-07-01 22:07:58", "2026-07-01 22:28:25",
+			53490.9, 53490.9, 3, "2026-07-01 22:28:25",
 		))
 
 	handler := NewMetricHandler(NewMetricRepository(db))
@@ -89,6 +89,9 @@ func TestMetricHandlerReturnsDailyMetrics(t *testing.T) {
 			t.Fatalf("response missing %s: %s", want, body)
 		}
 	}
+	if strings.Contains(body, "created_at") {
+		t.Fatalf("daily mileage response should not expose created_at: %s", body)
+	}
 	if err := mock.ExpectationsWereMet(); err != nil {
 		t.Fatalf("sql expectations: %v", err)
 	}
@@ -103,12 +106,12 @@ func TestMetricHandlerReturnsEmptyItemsArrayWhenNoRows(t *testing.T) {
 	mock.ExpectQuery("SELECT COUNT\\(\\*\\) FROM vehicle_daily_mileage").
 		WithArgs("YUTONG_MQTT").
 		WillReturnRows(sqlmock.NewRows([]string{"total"}).AddRow(0))
-	mock.ExpectQuery("SELECT 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").
+	mock.ExpectQuery("SELECT vin, stat_date, protocol, daily_mileage_km, first_total_mileage_km, latest_total_mileage_km, sample_count, updated_at FROM vehicle_daily_mileage").
 		WithArgs("YUTONG_MQTT", 50, 0).
 		WillReturnRows(sqlmock.NewRows([]string{
 			"vin", "stat_date", "protocol", "daily_mileage_km",
 			"first_total_mileage_km", "latest_total_mileage_km", "sample_count",
-			"created_at", "updated_at",
+			"updated_at",
 		}))
 
 	handler := NewMetricHandler(NewMetricRepository(db))

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

@@ -1,7 +1,6 @@
 package stats
 
 const DailyMileageTableSQL = `CREATE TABLE IF NOT EXISTS vehicle_daily_mileage (
-  id BIGINT PRIMARY KEY AUTO_INCREMENT,
   vin VARCHAR(32) NOT NULL,
   stat_date DATE NOT NULL,
   protocol VARCHAR(32) NOT NULL,
@@ -9,9 +8,8 @@ const DailyMileageTableSQL = `CREATE TABLE IF NOT EXISTS vehicle_daily_mileage (
   first_total_mileage_km DECIMAL(18,3) NULL,
   latest_total_mileage_km DECIMAL(18,3) NULL,
   sample_count BIGINT NOT NULL DEFAULT 0,
-  created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
   updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
-  UNIQUE KEY uk_daily_mileage_vin (vin, stat_date, protocol),
+  PRIMARY KEY (vin, stat_date, protocol),
   KEY idx_vin (vin),
   KEY idx_stat_date (stat_date),
   KEY idx_protocol_date (protocol, stat_date)