EntityFramework中使用Include可能帶來的問題

本文轉載自查看原文 2012-03-09 16:43 4526 學習筆記

這個問題是在處理層級查詢上出現的，按照以前的經驗當查詢A以及A的子集合B[]的時候join一下比分兩次查詢快，但是當子集合比較多等原因的時候時間不是線性增長而是指數，原因應該是重復數據帶來的效率負載增加，比如第一種我的單元測試時間Duration在4-6左右，當增加到3個子集合的時候就在14-22之間了，而Ef中的做法是把每個join結果unicon 起來，看着那么大串的數據不慢才怪，還是乖乖分開了。

時間如圖：

測試代碼：

     public class ModelTesting
    {
         private EFContext _dbContext;
         public ModelTesting()
        {
             string cnn = System.Configuration.ConfigurationManager.ConnectionStrings[ 0].ConnectionString;

            _dbContext = new EFContext(cnn);

        }
        [Fact]
         public void Test()
        {
             var key = 1000;
             var uid = new Guid( " 3905858E-A32E-DF11-BA8F-001CF0CD104B ");
             var myResume = _dbContext.Set<MyUser>()
                .Single(u => u.UserId == uid);
            myResume.Works.ToList();
            myResume.Resumes.ToList();
            myResume.Projects.ToList();
            myResume.Jobs.ToList();
            myResume=_dbContext.Set<MyUser>()
                .Include( " Resumes ")
                .Include( " Jobs ")
                .Include( " Projects ")
                .Include( " Works ")
                .Single(u => u.UserId == uid);

        }
    }

     public class EFContext:DbContext
    {
         public EFContext( string cnn): base(cnn)
        {
             this.Configuration.LazyLoadingEnabled = true;
        }

         protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
             base.OnModelCreating(modelBuilder);
            modelBuilder.Entity<MyResume>();
            modelBuilder.Entity<MyWorkExper>();
            modelBuilder.Entity<MyProject>();
            modelBuilder.Entity<MyUser>();
        }
    }
    [Table( " Resume ", Schema = " dbo ")]
     public class MyResume
    {
        [Key]
         public int Key { get; set; }
        [ForeignKey( " Owner ")]
         public Guid UserId { get; set; }
         public MyUser Owner { get; set; }
    }

    [Table( " WorkExperience ", Schema = " Resume ")]
     public class MyWorkExper
    {
        [Key]
         public int WorkId { get; set; }
        [ForeignKey( " Owner ")]
         public Guid UserId { get; set; }
         public MyUser Owner { get; set; }
    }
        [Table( " project ",Schema = " Resume ")]
     public class MyProject
        {
            [Key]
             public int ProjectId { get; set; }
            [ForeignKey( " Owner ")]
             public Guid UserId { get; set; }
             public MyUser Owner { get; set; }
        }
    [Table( " EnterpriseUser ", Schema = " Offer ")]
     public   class MyUser
    {
        [Key]
        [Column( " UserGuid ")]
         public Guid UserId { get; set; }
         public virtual ICollection<MyResume> Resumes { get; set; }
         public virtual ICollection<MyProject> Projects { get; set; }
         public virtual ICollection<MyWorkExper> Works { get; set; }
         public virtual ICollection<MyJob> Jobs { get; set; }
    }
    [Table( " Offer ", Schema = " Offer ")]
     public class MyJob
    {
        [Key]
         public long Key
        {
             get;
             set;
        }
        [ForeignKey( " Owner ")]
        [Required]
         public Guid UserID { get; set; }

         public virtual MyUser Owner { get; set; }
    }

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