这个问题是在处理层级查询上出现的，按照以前的经验当查询A以及A的子集合B[]的时候join一下比分两次查询快，但是当子集合比较多等原因的时候时间不是线性增长而是指数，原因应该是重复数据带来的效率负载增加，比如第一种我的单元测试时间Duration在4-6左右，当增加到3个子集合的时候就在14-22之间了，而Ef中的做法是把每个join结果unicon 起来，看着那么大串的数据不慢才怪，还是乖乖分开了。

 

 时间如图：

 

测试代码：

    

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; }

    }