Question

我正在使用MVC5和EF6来开发应用程序。我正在使用SQL Server Express作为数据库。我在数据库中有两个表/实体。

车辆 - 包含有关车辆的信息
VehicleLog - 包含从车辆中的GPS Tracker Fit收到的数据。

我的VehicleLog表目前有大约20K的记录，从特定车辆的表中获取数据大约需要80秒。例如：我尝试获取最后一条记录以显示车辆的当前状态（即移动或停止），并且需要超过1分半钟。

车辆日志表中的记录数量会随着时间的推移而增加。

当我尝试使用Server explorer打开表时，它会在5-10秒内显示所有数据。任何人都可以帮助我在页面上快速加载详细信息。

感谢阅读和关注这个问题。

我的代码：

 public ActionResult Dashboard()
    {
        ApplicationUser au = db.Users.Find(currentUser);

        var myVehicles = from vehicle in au.Vehicles.ToList()
                         where vehicle.License.ExpiryDate >= DateTime.Now && !vehicle.IsDeleted
                         select new CurrentVehicleStatus
                         {
                             VehicleName = vehicle.Name,
                             DriverName = vehicle.Driver != null ? vehicle.Driver.Name : "No driver",
                             DriverId=vehicle.Driver != null ? vehicle.Driver.DriverId : 0,
                             VehicleId = vehicle.VehicleId,
                             VehicleStatus = GeoUtils.GetStatusOf(vehicle.GsmDeviceLogs.Last())
                          };
    return PartialView("Dashboard", myVehicles);
    }


public static VehicleStatus GetStatusOf(GSMDeviceLog deviceLog)
    {
        VehicleStatus currentStatus = VehicleStatus.Stop;

        if (deviceLog != null)
        {
            //Considering DigitalInputLevel1 as Ignition. Not a correct way to do it as DigitalInputLevel1
            //is device dependent. Must change in future.
            if (deviceLog.DigitalInputLevel1)
                currentStatus = VehicleStatus.Idle;

            if (deviceLog.DigitalInputLevel1 && deviceLog.Speed > ZERO_SPEED)
                currentStatus = VehicleStatus.Moving;
            else if (!deviceLog.DigitalInputLevel1 && deviceLog.Speed >= ZERO_SPEED)
                currentStatus = VehicleStatus.Towed;
            if ((DateTime.Now - deviceLog.DateTimeOfLog).TotalMinutes > 2)
                currentStatus = VehicleStatus.Unreachable;
        }
        else
            currentStatus = VehicleStatus.Unreachable;

        return currentStatus;
    }

如果我评论最后一行（VehicleStats = ....）页面的加载时间低于1秒。但如果它在2分钟左右发表评论。

型号：

public class Vehicle
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int VehicleId
    { get; set; }

    [Display(Name = "Vehicle name")]
    [StringLength(100)]
    public String Name
    { get; set; }

    [Required]
    public String VehicleType
    { get; set; }

    [Required]
    [StringLength(20)]
    [Display(Name = "Registration no.")]
    public String RegNo
    { get; set; }

    [Required]
    [StringLength(100)]
    public String Manufacturer
    { get; set; }

    [StringLength(20)]
    [Display(Name = "Model or Year")]
    public String Year
    { get; set; }

    [StringLength(100)]
    [Display(Name = "Service provider")]
    public String ServiceProvider
    { get; set; }

    [DataType(DataType.Date)]
    [Display(Name = "Insurance date")]
    [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}", ApplyFormatInEditMode = true)]
    public DateTime InsuranceDate
    { get; set; }

    [DataType(DataType.Date)]
    [Display(Name = "Last serviced on")]
    public DateTime LastServicedOn
    { get; set; }

    [Display(Name = "Last serviced at (km)")]
    public int LastServicedAt
    { get; set; }

    [Display(Name = "Next service at (km)")]
    public int NextServiceAt
    { get; set; }

    [DataType(DataType.Date)]
    [Display(Name = "PUC expiry date")]
    public DateTime PUCExpiryDate
    { get; set; }


    [Display(Name = "Vehicle Ownership document")]
    [DataType(DataType.ImageUrl)]
    public virtual List<OwnershipPaper> OwnershipPapers
    { get; set; }

    //[Display(Name = "Vehicle status")]
    //public VehicleStatusType VehicleStatus
    //{ get; set; }

    [Display(Name = "Target Utilization (km) per day")]
    public int TargetUtilizationPerDay
    { get; set; }

    public virtual Driver Driver
    { get; set; }
    [Display(Name = "Vehicle Group")]

    [Required]
    public virtual VehicleGroup VehicleGroup
    { get; set; }

    public string IMEI 
    { get; set; }

    [Display(Name="Fuel tank capacity")]
    [Required]
    public double FuelTankCapacityLitres
    { get; set; }

    public virtual License License { get; set; }

    public virtual ICollection<GSMDeviceLog> GsmDeviceLogs { get; set; }

    public virtual Policy Policy { get; set; }

    public virtual ApplicationUser User { get; set; }

    public bool IsDeleted { get; set; }
}



public class GSMDeviceLog
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int GSMDeviceLogId { get; set; }
    public string IMEI { get; set; }
    public string Message { get; set; }
    public string ProfileName { get; set; }
    public bool GPSStatus { get; set; }
    public int SignalStrength { get; set; }
    public DateTime DateTimeOfLog { get; set; }
    //public string TimeOfLog { get; set; }
    public double Latitude { get; set; }
    public double Longitude { get; set; }
    public float Altitude { get; set; }
    public float Speed { get; set; }
    public float Direction { get; set; }
    public int NoOfSatelite { get; set; }
    public float GPSPositionAccuracyIndication { get; set; }
    public float MilageReading { get; set; }
    public string Cell { get; set; }
    public float AnalogInputVoltage1 { get; set; }
    public float AnalogInputVoltage2 { get; set; }
    public float AnalogInputVoltage3 { get; set; }
    public float AnalogInputVoltage4 { get; set; }
    public bool DigitalInputLevel1 { get; set; }
    public bool DigitalInputLevel2 { get; set; }
    public bool DigitalInputLevel3 { get; set; }
    public bool DigitalInputLevel4 { get; set; }
    public bool DigitalOutputLevel1 { get; set; }
    public bool DigitalOutputLevel2 { get; set; }
    public bool DigitalOutputLevel3 { get; set; }
    public bool DigitalOutputLevel4 { get; set; }

    [Display(Name="Address")]
    public string Location { get; set; }

    public int InfoNumber { get; set; }

    //Reperesent harsh accelration and deaccelration
    public bool HarshDetecation { get; set; }

    //RFID Tag Number
    [StringLength(15)]
    public string RFID { get; set; }

    //public virtual Policy Policy { get; set; }

    public virtual ICollection<Violation> Violations { get; set; }

    public virtual Vehicle Vehicle { get; set; }


}

Answer 1

问题是你对ToList（）的调用。这将评估查询并从数据库中检索每一行。

然后在循环中调用导航属性。这将导致为数据库中的每个项执行新查询。这是运行缓慢的原因。

如果您只是将'ToList（）'调用移到'select'语句之后，那么所有问题都将得到解决。

myVehicles = from vehicle in au.Vehicles
    where vehicle.License.ExpiryDate >= DateTime.Now && !vehicle.IsDeleted
    select new
    {
        VehicleName = vehicle.Name,
        DriverName = vehicle.Driver.Name ?? "No driver",
        DriverId= vehicle.Driver == null ? 0 : vehicle.Driver.DriverId,
        VehicleId = vehicle.VehicleId,
        GsmDeviceLogs = vehicle.GsmDeviceLogs.LastOrDefault()
    }.ToList()
    .Select({vehicle => new CurrentVehicleStatus
        VehicleName = VehicleName,
        DriverName = DriverName,
        DriverId= DriverId,
        VehicleId = VehicleId,
        VehicleStatus = GeoUtils.GetStatusOf(GsmDeviceLogs)
    });

编辑：将三元运算符更改为空合并以使它们对EntityFramework友好（如果Driver为null则无关紧要，因为这是一个在后台转换为SQL的表达式）。

编辑：看过GeoUtils的代码，更新了答案。它肯定不会在表达式树中解析。此外，更改了对LastOrDefault（）的调用。

Answer 2

您的查询实际上是LINQ to Objects in memory而不是数据库查询（LINQ to Entities），因为源集合是au.Vehicles，它是内存中的集合。但是，由于延迟加载，涉及多个数据库查询，这些查询加载的数据远远超过您在幕后所需的数据：

au.Vehicles已延迟加载，即用户au的所有车辆 - ＆gt; 1个数据库查询
Vehicle.License已延迟加载 - ＆gt;每辆车1个数据库查询（满足where过滤器）
Vehicle.Driver已延迟加载 - ＆gt;每辆车1个数据库查询（满足where过滤器）
Vehicle.GsmDeviceLogs已延迟加载，即所有车辆日志 - ＆gt;每辆车1个数据库查询（满足where过滤器）

所有这些延迟加载查询很可能是性能不佳的原因。

为确保整个内容只是一个只加载所需数据的数据库查询，您必须尽可能多地从DbSet<T>/IQueryable<T>编写查询。在您的情况下，尤其要避免Find的{{1}}。它看起来像这样：

ApplicationUser

正如Max所提到的，var myVehicles = db.Users .Where(u => u.UserName == currentUser) .SelectMany(u => u.Vehicles) .Where(v => v.License.ExpiryDate >= DateTime.Now && !v.IsDeleted) .Select(v => new { VehicleName = v.Name, DriverName = v.Driver != null ? v.Driver.Name : "No driver", DriverId = v.Driver != null ? v.Driver.DriverId : 0, VehicleId = v.VehicleId, LastGsmDeviceLog = v.GsmDeviceLogs .OrderByDescending(gdl => gdl.CreateDateTime) .FirstOrDefault() }) .AsEnumerable() .Select(x => new CurrentVehicleStatus { VehicleName = x.VehicleName, DriverName = x.DriverName, DriverId = x.DriverId, VehicleId = x.VehicleId, VehicleStatus = GeoUtils.GetStatusOf(x.LastGsmDeviceLog) });无法转换为SQL，因此您必须使用GeoUtils.GetStatusOf结束数据库查询（其内存开销小于AsEnumerable()）并执行最终ToList()并在内存中调用Select。

Answer 3

它会做很多提取。尝试Max方法，但将LastOrDefault（）更改为无法转换为SQL到OrderBy和FirstOrDefault。像这样的东西

myVehicles = from vehicle in au.Vehicles
where vehicle.License.ExpiryDate >= DateTime.Now && !vehicle.IsDeleted
select new
{
    VehicleName = vehicle.Name,
    DriverName = vehicle.Driver.Name ?? "No driver",
    DriverId= vehicle.Driver == null ? 0 : vehicle.Driver.DriverId,
    VehicleId = vehicle.VehicleId,
    GsmDeviceLogs = vehicle.GsmDeviceLogs.OrderByDescending(l => l.Id).FirstOrDefault()
}.ToList()
.Select({vehicle => new CurrentVehicleStatus
    VehicleName = VehicleName,
    DriverName = DriverName,
    DriverId= DriverId,
    VehicleId = VehicleId,
    VehicleStatus = GeoUtils.GetStatusOf(GsmDeviceLogs)
});

结果应该是'外部应用'SQL语法。

加载时间太长

3 个答案: