perf(query): 优化后台手机号精确查询

backend/internal/modules/order/queries.go

@@ -241,7 +241,7 @@ func (r *Repository) adminOrderCountQuery(ctx context.Context, query AdminOrderQ
 	upper := strings.ToUpper(kw)
 	needsJoin := false
 	if kw != "" {
-		if strings.HasPrefix(upper, "RO") || strings.HasPrefix(upper, "ORD") {
+		if isPhoneKeyword(kw) || strings.HasPrefix(upper, "RO") || strings.HasPrefix(upper, "ORD") {
 			needsJoin = false
 		} else if id, err := strconv.ParseUint(kw, 10, 64); err == nil && id > 0 && kw[0] != '0' && len(kw) < 9 {
 			needsJoin = false
@@ -334,9 +334,14 @@ func applyAdminOrderFilters(db *gorm.DB, query AdminOrderQuery) *gorm.DB {
 	}
 	if keyword := strings.TrimSpace(query.Keyword); keyword != "" {
 		upper := strings.ToUpper(keyword)
-		if len(keyword) == 11 && keyword[0] == '1' && isAllDigits(keyword) {
-			// 11 位手机号：命中 users(phone) 唯一索引
-			db = db.Where("(owner.phone = ? OR renter.phone = ?)", keyword, keyword)
+		if isPhoneKeyword(keyword) {
+			// 先由 users(phone) 唯一索引解析用户，再让订单表 owner_id/renter_id 索引驱动。
+			// 不能直接写 owner.phone/renter.phone：跨表别名 OR 会让 MySQL 倒序扫描全部订单。
+			db = db.Where(
+				"(o.owner_id = (SELECT id FROM users WHERE phone = ?) OR o.renter_id = (SELECT id FROM users WHERE phone = ?))",
+				keyword,
+				keyword,
+			)
 		} else if strings.HasPrefix(upper, "RO") || strings.HasPrefix(upper, "ORD") {
 			// 订单号：命中 rental_orders(order_no) 唯一索引
 			db = db.Where("o.order_no = ?", keyword)
@@ -532,3 +537,7 @@ func isAllDigits(s string) bool {
 	}
 	return len(s) > 0
 }
+
+func isPhoneKeyword(s string) bool {
+	return len(s) == 11 && s[0] == '1' && isAllDigits(s)
+}