我在一个全新的项目上有这个简单的模型:
class A
{
public int Id { get; set; }
public B B { get; set; }
}
class B
{
public int Id { get; set; }
public string Text { get; set; }
}
class C
{
public int Id { get; set; }
public B B { get; set; }
}
映射是:
modelBuilder.Entity<A>().HasOptional(x => x.B).WithOptionalDependent();
modelBuilder.Entity<C>().HasOptional(x => x.B).WithOptionalDependent();
我正在运行此查询:
db.As.Include(a => a.B).Where(a => a.B.Text == "10").FirstOrDefault();
其中db.As
是A的DbSet。
它生成以下sql
SELECT TOP (1)
[Extent1].[Id] AS [Id],
[Join8].[Id1] AS [Id1],
[Join8].[Text] AS [Text],
[Join11].[Id2] AS [Id2],
[Join14].[Id3] AS [Id3]
FROM [dbo].[A] AS [Extent1]
INNER JOIN (SELECT [Extent2].[Text] AS [Text], [Extent3].[Id] AS [Id4]
FROM [dbo].[B] AS [Extent2]
LEFT OUTER JOIN [dbo].[A] AS [Extent3] ON ([Extent3].[B_Id] IS NOT NULL) AND ([Extent2].[Id] = [Extent3].[B_Id])
LEFT OUTER JOIN [dbo].[C] AS [Extent4] ON ([Extent4].[B_Id] IS NOT NULL) AND ([Extent2].[Id] = [Extent4].[B_Id]) ) AS [Join2] ON [Extent1].[Id] = [Join2].[Id4]
INNER JOIN (SELECT [Extent5].[Text] AS [Text], [Extent6].[Id] AS [Id5]
FROM [dbo].[B] AS [Extent5]
LEFT OUTER JOIN [dbo].[A] AS [Extent6] ON ([Extent6].[B_Id] IS NOT NULL) AND ([Extent5].[Id] = [Extent6].[B_Id])
LEFT OUTER JOIN [dbo].[C] AS [Extent7] ON ([Extent7].[B_Id] IS NOT NULL) AND ([Extent5].[Id] = [Extent7].[B_Id]) ) AS [Join5] ON [Extent1].[Id] = [Join5].[Id5]
LEFT OUTER JOIN (SELECT [Extent8].[Id] AS [Id1], [Extent8].[Text] AS [Text], [Extent9].[Id] AS [Id6]
FROM [dbo].[B] AS [Extent8]
LEFT OUTER JOIN [dbo].[A] AS [Extent9] ON ([Extent9].[B_Id] IS NOT NULL) AND ([Extent8].[Id] = [Extent9].[B_Id])
LEFT OUTER JOIN [dbo].[C] AS [Extent10] ON ([Extent10].[B_Id] IS NOT NULL) AND ([Extent8].[Id] = [Extent10].[B_Id]) ) AS [Join8] ON [Extent1].[Id] = [Join8].[Id6]
LEFT OUTER JOIN (SELECT [Extent12].[Id] AS [Id2]
FROM [dbo].[B] AS [Extent11]
LEFT OUTER JOIN [dbo].[A] AS [Extent12] ON ([Extent12].[B_Id] IS NOT NULL) AND ([Extent11].[Id] = [Extent12].[B_Id])
LEFT OUTER JOIN [dbo].[C] AS [Extent13] ON ([Extent13].[B_Id] IS NOT NULL) AND ([Extent11].[Id] = [Extent13].[B_Id]) ) AS [Join11] ON [Extent1].[Id] = [Join11].[Id2]
LEFT OUTER JOIN (SELECT [Extent15].[Id] AS [Id7], [Extent16].[Id] AS [Id3]
FROM [dbo].[B] AS [Extent14]
LEFT OUTER JOIN [dbo].[A] AS [Extent15] ON ([Extent15].[B_Id] IS NOT NULL) AND ([Extent14].[Id] = [Extent15].[B_Id])
LEFT OUTER JOIN [dbo].[C] AS [Extent16] ON ([Extent16].[B_Id] IS NOT NULL) AND ([Extent14].[Id] = [Extent16].[B_Id]) ) AS [Join14] ON [Extent1].[Id] = [Join14].[Id7]
WHERE (N'10' = [Join2].[Text]) AND ([Join5].[Text] IS NOT NULL)
这对我来说似乎很复杂。它甚至与C“连接”,我没有从A和B引用它,并且不包括在查询中。
现在,事情是:我们有一个包含一些非常复杂模型的大型项目,我们遇到了一些性能问题,当我们查询查询时,我们发现有些查询需要“包含”很多实体,生成超过3k行的SQL。
我们的映射或配置是否有问题?我们禁用了延迟加载和代理创建。
答案 0 :(得分:3)
我没有真正的答案,但我会写相同的规格:
modelBuilder.Entity<A>().HasOptional(x => x.B).WithMany();
modelBuilder.Entity<C>().HasOptional(x => x.B).WithMany();
提供与您相同的数据库架构。
为什么我会这样做:因为我经常考虑“我想要什么架构?”,并且通过我的实践,对于这个架构,代码就是上面那个。
BTW:ctx.Set<A>().Include(x => x.B).Where(x => x.B.Text == "10").Select(x => x)
的结果查询是:
SELECT
[Extent1].[Id] AS [Id],
[Extent3].[Id] AS [Id1],
[Extent3].[Text] AS [Text]
FROM
[dbo].[A] AS [Extent1]
INNER JOIN [dbo].[B] AS [Extent2] ON [Extent1].[B_Id] = [Extent2].[Id]
LEFT OUTER JOIN [dbo].[B] AS [Extent3] ON [Extent1].[B_Id] = [Extent3].[Id]
WHERE
N'10' = [Extent2].[Text]
但仍然在这里:为什么要延伸3?
因为Extend2允许过滤没有B的A:inner join ... extend2
是一个地方(真的很清楚,没有?)