.net - 具有非常相似查询的 EF 性能非常不同

Question

我们有两个 Entity Framework 查询，一个是 Include一种带有独立查询的。他们来了

        ConfigModelContainer model = new ConfigModelContainer();
        var scope = model.Scopes.Include("Settings")
            .Where(s => (s.Level == intLevel && s.Name == name))
            .First();

        ConfigModelContainer model = new ConfigModelContainer();
        var scope = model.Scopes
            .Where(s => (s.Level == intLevel && s.Name == name))
            .First();
        var settings = model.Settings.Where(s => s.Scope.Id == scope.Id).ToList();

另一个与第一个 (Query2) 具有相同性能的案例

        var scope1 = model.Scopes
            .Where(s => (s.Level == intLevel && s.Name == name))
            .First();
        scope1.Settings.Load();

第一个运行 30 秒，第二个运行亚秒。这太奇怪了，我没有想法。

有谁知道为什么会发生这种情况？

编辑 :实际的 TSQL 查询运行速度非常快(亚秒级)

编辑 2 : 以下是查询:

第一的:

SELECT 
[Project2].[Level] AS [Level], 
[Project2].[Id] AS [Id], 
[Project2].[Name] AS [Name], 
[Project2].[ParentScope_Id] AS [ParentScope_Id], 
[Project2].[C1] AS [C1], 
[Project2].[Id1] AS [Id1], 
[Project2].[Type] AS [Type], 
[Project2].[Value] AS [Value], 
[Project2].[Scope_Id] AS [Scope_Id]
FROM ( SELECT 
    [Limit1].[Id] AS [Id], 
    [Limit1].[Name] AS [Name], 
    [Limit1].[Level] AS [Level], 
    [Limit1].[ParentScope_Id] AS [ParentScope_Id], 
    [Extent2].[Id] AS [Id1], 
    [Extent2].[Type] AS [Type], 
    [Extent2].[Value] AS [Value], 
    [Extent2].[Scope_Id] AS [Scope_Id], 
    CASE WHEN ([Extent2].[Id] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
    FROM   (SELECT TOP (1) 
        [Extent1].[Id] AS [Id], 
        [Extent1].[Name] AS [Name], 
        [Extent1].[Level] AS [Level], 
        [Extent1].[ParentScope_Id] AS [ParentScope_Id]
        FROM [dbo].[Scopes] AS [Extent1]
        WHERE ([Extent1].[Level] = @p__linq__0) AND ([Extent1].[Name] = @p__linq__1) ) AS [Limit1]
    LEFT OUTER JOIN [dbo].[Settings] AS [Extent2] ON [Limit1].[Id] = [Extent2].[Scope_Id]
)  AS [Project2]
ORDER BY [Project2].[Id] ASC, [Project2].[C1] ASC

第二:

SELECT 
[Limit1].[Level] AS [Level], 
[Limit1].[Id] AS [Id], 
[Limit1].[Name] AS [Name], 
[Limit1].[ParentScope_Id] AS [ParentScope_Id]
FROM ( SELECT TOP (1) 
    [Extent1].[Id] AS [Id], 
    [Extent1].[Name] AS [Name], 
    [Extent1].[Level] AS [Level], 
    [Extent1].[ParentScope_Id] AS [ParentScope_Id]
    FROM [dbo].[Scopes] AS [Extent1]
    WHERE ([Extent1].[Level] = @p__linq__0) AND ([Extent1].[Name] = @p__linq__1)
)  AS [Limit1]

SELECT 
1 AS [C1], 
[Extent1].[Id] AS [Id], 
[Extent1].[Type] AS [Type], 
[Extent1].[Value] AS [Value], 
[Extent1].[Scope_Id] AS [Scope_Id]
FROM [dbo].[Settings] AS [Extent1]
WHERE [Extent1].[Scope_Id] = @EntityKeyValue1

第三:

SELECT 
[Limit1].[Level] AS [Level], 
[Limit1].[Id] AS [Id], 
[Limit1].[Name] AS [Name], 
[Limit1].[ParentScope_Id] AS [ParentScope_Id]
FROM ( SELECT TOP (1) 
    [Extent1].[Id] AS [Id], 
    [Extent1].[Name] AS [Name], 
    [Extent1].[Level] AS [Level], 
    [Extent1].[ParentScope_Id] AS [ParentScope_Id]
    FROM [dbo].[Scopes] AS [Extent1]
    WHERE ([Extent1].[Level] = @p__linq__0) AND ([Extent1].[Name] = @p__linq__1)
)  AS [Limit1]

SELECT 
1 AS [C1], 
[Extent1].[Id] AS [Id], 
[Extent1].[Type] AS [Type], 
[Extent1].[Value] AS [Value], 
[Extent1].[Scope_Id] AS [Scope_Id]
FROM [dbo].[Settings] AS [Extent1]
WHERE [Extent1].[Scope_Id] = @p__linq__0

编辑 3 :

我无法在同一台机器上继续测试。这是在更快的机器上的结果。这是代码和结果:

    static void Main(string[] args)
    {
        int intLevel = 2;
        string name = "fb226050-4f92-4fca-9442-f76565b33877";
        Stopwatch sw = new Stopwatch();
        using (CMEntities model = new CMEntities())
        {
            sw.Start();
            for (int i = 0; i < 5; i++)
            {

                var scope1 = model.Scopes.Include("Settings")
                   .Where(s => (s.Level == intLevel && s.Name == name))
                   .First();

                Console.WriteLine("Query:1, Iter:{0}, Time:{1}", i, sw.ElapsedMilliseconds);
                sw.Reset();
                sw.Start();
            }
        }
        Console.WriteLine();
        using (CMEntities model = new CMEntities())
        {
            sw.Start();
            for (int i = 0; i < 5; i++)
            {

                var scope1 = model.Scopes
                   .Where(s => (s.Level == intLevel && s.Name == name))
                   .First();
                scope1.Settings.Load();
                Console.WriteLine("Query:2, Iter:{0}, Time:{1}", i, sw.ElapsedMilliseconds);
                sw.Reset();
                sw.Start();
            }
        }
        Console.WriteLine();
        using (CMEntities model = new CMEntities())
        {
            for (int i = 0; i < 5; i++)
            {
                var scope = model.Scopes
                    .Where(s => (s.Level == intLevel && s.Name == name))
                    .First();
                var settings = model.Settings.Where(s => s.Scope.Id == scope.Id).ToList();
                Console.WriteLine("Query:3, Iter:{0}, Time:{1}", i, sw.ElapsedMilliseconds);
                sw.Reset();
                sw.Start();
            }                
        }
    }
    }

结果:

Query:1, Iter:0, Time:2477
Query:1, Iter:1, Time:1831
Query:1, Iter:2, Time:1933
Query:1, Iter:3, Time:1774
Query:1, Iter:4, Time:1949

Query:2, Iter:0, Time:2036
Query:2, Iter:1, Time:1870
Query:2, Iter:2, Time:1921
Query:2, Iter:3, Time:1751
Query:2, Iter:4, Time:1758

Query:3, Iter:0, Time:188
Query:3, Iter:1, Time:201
Query:3, Iter:2, Time:185
Query:3, Iter:3, Time:203
Query:3, Iter:4, Time:217

编辑 4 : 我用 NHibernate 重写了代码:

    static void Main(string[] args)
    {

        var cfg = new StoreConfiguration();
        var sessionFactory = Fluently.Configure()
          .Database(MsSqlConfiguration.MsSql2005
              .ConnectionString("Data Source=.;Initial Catalog=CM;Integrated Security=True;MultipleActiveResultSets=True")
          )
          .Mappings(m =>
                m.AutoMappings.Add(
                    AutoMap.AssemblyOf<Entities.Scope>(cfg)
                        .Conventions
                            .Add(
                                Table.Is(x => x.EntityType.Name + "s"),
                                PrimaryKey.Name.Is(x => "Id"),
                                ForeignKey.EndsWith("_id")
                            )
                    )
          )             
          .BuildSessionFactory();
        Stopwatch sw = new Stopwatch();
        for (int i = 0; i < 5; i++)
        {
            sw.Start();
            var session = sessionFactory.OpenSession();
            int intLevel = 2;
            string name = "fb226050-4f92-4fca-9442-f76565b33877";
            var scope = session.CreateCriteria<Entities.Scope>()
                .SetFetchMode("Settings", FetchMode.Eager)
                .Add(Restrictions.Eq("Name", name))
                .Add(Restrictions.Eq("Level", intLevel))                    
                .UniqueResult<Entities.Scope>();
            Console.WriteLine("Query:0, Iter:{0}, Time:{1}", i, sw.ElapsedMilliseconds);
            sw.Reset();
        }
    }

结果是:

Query:0, Iter:0, Time:446
Query:0, Iter:1, Time:223
Query:0, Iter:2, Time:303
Query:0, Iter:3, Time:275
Query:0, Iter:4, Time:284

因此 NHibernate 形成正确集合的速度比 EF 快 10 倍。这真的很可悲。

这是 NHibernate 生成的查询:

SELECT this_.id            AS id0_1_, 
       this_.name          AS name0_1_, 
       this_.LEVEL         AS level0_1_, 
       settings2_.scope_id AS scope4_3_, 
       settings2_.id       AS id3_, 
       settings2_.id       AS id1_0_, 
       settings2_.TYPE     AS type1_0_, 
       settings2_.VALUE    AS value1_0_, 
       settings2_.scope_id AS scope4_1_0_ 
FROM   scopes this_ 
       LEFT OUTER JOIN settings settings2_ 
         ON this_.id = settings2_.scope_id 
WHERE  this_.name = @p0 
       AND this_.LEVEL = @p1 

Answer 1

有几件事要检查...

实体模型中 Scopes 和 Settings 之间的关系是如何定义的？是否使用了正确的外键？多重性如何(一对多等)？

如果您将第一个查询更改为:

，您的执行时间是否会有所改善？

.

ConfigModelContainer model = new ConfigModelContainer();
var scope = model.Scopes.Include("Settings")
                 .First<Scope>(s => s.Level == intLevel && s.Name == name);

我不确定 Linq 是否会优化与您不同的查询，但也许看看它是否会这样做。

至于升级到 EF 4.0，我不知道如果您的项目是在 .NET 3.5 中，这有多可行。尽管如此，当我们的项目使用 .NET 3.5/EF 1 时，我从未遇到过这个问题。