Question

我有以下抽象类：

public abstract class Notification
{
    public Notification()
    {
        this.receivedDate = DateTime.Now.ToUniversalTime();
    }

    public int Id { get; set; }

    public DateTime receivedDate { get; set; }

    public bool unread { get; set; }

    public virtual ApplicationUser recipient { get; set; }
}

有几个类继承自它，例如ProfileViewNotification和NewMessageNotification：

public class ProfileViewNotification: Notification
{
    public virtual ApplicationUser Viewer { get; set; }
}

public class NewMessageNotification: Notification
{
    public virtual Message Message { get; set; }
}

我有以下方法在我的数据库中查询具有给定Notification ApplicationUser的所有recipient：

public static List<NotificationApiViewModel> GetNotificationsForUser(string idOfUser)
    {
        List<NotificationApiViewModel> resultAsApiViewModel = new List<NotificationApiViewModel>();

        List<ProfileViewNotification> ofProfileViewNotificationType = null;
        List<NewMessageNotification> ofNewMessageNotificationType = null;

        try
        {
            using (var context = new ApplicationDbContext())
            {
                var query = context.Notifications.Where(c => c.recipient.Id == idOfUser);

                ofNewMessageNotificationType = query.OfType<NewMessageNotification>().Any() ? 
                    query.OfType<NewMessageNotification>()
                    .Include(n => n.recipient)
                    .Include(n => n.recipient.MyProfile)
                    .Include(n => n.recipient.MyProfile.ProfileImages)
                    .Include(n => n.Message)
                    .Include(n => n.Message.Author)
                    .Include(n => n.Message.Author.MyProfile)
                    .Include(n => n.Message.Author.MyProfile.ProfileImages)
                    .Include(n => n.Message.Recipient)
                    .Include(n => n.Message.Recipient.MyProfile)
                    .Include(n => n.Message.Recipient.MyProfile.ProfileImages)
                    .ToList() 
                    : null;

                ofProfileViewNotificationType = query.OfType<ProfileViewNotification>().Any() ? 
                    query.OfType<ProfileViewNotification>()
                    .Include(n => n.recipient)
                    .Include(n => n.recipient.MyProfile)
                    .Include(n => n.recipient.MyProfile.ProfileImages)
                    .Include(n => n.Viewer)
                    .Include(n => n.Viewer.MyProfile)
                    .Include(n => n.Viewer.MyProfile.ProfileImages)
                    .ToList() 
                    : null;

                }

        }
        catch (Exception ex)
        {
            //Log issue
        }

        if (ofNewMessageNotificationType != null)
        {
            foreach (var n in ofNewMessageNotificationType)
            {
                resultAsApiViewModel.Add(NotificationApiViewModel.ConvertToApiViewModel(n));
            }
        }

        if (ofProfileViewNotificationType != null)
        {
            foreach (var n in ofProfileViewNotificationType)
            {
                resultAsApiViewModel.Add(NotificationApiViewModel.ConvertToApiViewModel(n));
            }
        }

        return resultAsApiViewModel;
    }

重要的是要注意，我的ConvertToApiViewModel方法都没有查询数据库，这就是我在原始查询中拥有所有这些Include的原因。此外，为简洁起见，上面仅包括两种类型的通知，但我总共有十几种。

我的问题是我的方法非常慢。对于只有20个通知的用户，需要一分钟才能完成！

任何人都可以告诉我我做错了什么？

Answer 1

您正在为数据库中的每个查询打电话，所以您可以做的就是将它们组合成一个查询，如下所示：

  try
            {
                using (var context = new ApplicationDbContext())
                {
                    //Here you execute the single query
                    var query = context.Notifications.Where(c => c.recipient.Id == idOfUser)
 .Include(n => n.recipient)
                        .Include(n => n.recipient.MyProfile)
                        .Include(n => n.recipient.MyProfile.ProfileImages)
                        .Include(n => n.Message)
                        .Include(n => n.Message.Author)
                        .Include(n => n.Message.Author.MyProfile)
                        .Include(n => n.Message.Author.MyProfile.ProfileImages)
                        .Include(n => n.Message.Recipient)
                        .Include(n => n.Message.Recipient.MyProfile)
                        .Include(n => n.Message.Recipient.MyProfile.ProfileImages)
.Include(n => n.Viewer)
                        .Include(n => n.Viewer.MyProfile)
                        .Include(n => n.Viewer.MyProfile.ProfileImages)
.ToList(); 

                    ofNewMessageNotificationType = query.OfType<NewMessageNotification>().Any() ? 
                        query.OfType<NewMessageNotification>(): null;

                    ofProfileViewNotificationType = query.OfType<ProfileViewNotification>().Any() ? 
                        query.OfType<ProfileViewNotification>() : null;

                    }

            }
            catch (Exception ex)
            {
                //Log issue
            }

            if (ofNewMessageNotificationType != null)
            {
                foreach (var n in ofNewMessageNotificationType)
                {
                    resultAsApiViewModel.Add(NotificationApiViewModel.ConvertToApiViewModel(n));
                }
            }

            if (ofProfileViewNotificationType != null)
            {
                foreach (var n in ofProfileViewNotificationType)
                {
                    resultAsApiViewModel.Add(NotificationApiViewModel.ConvertToApiViewModel(n));
                }
            }

            return resultAsApiViewModel;
        }

希望这会有所帮助......

Answer 2

感谢大家的意见和回复。为了记录我更快地查询的方式是使用query.Select(n => new DTO{})和Data Transfer Objects (DTOs)而不是我的多个Include。就这一点而言，我将性能提高了一个数量级。我还使查询异步，这进一步提高了性能。

查询速度很慢，我该如何改进呢？

2 个答案: