具有Linq性能问题的EntityFramework 6.1.1

Question

我正在使用EntityFramework从我的mssql数据库中选择数据.我的查询看起来像这样:

int param = 123456;
using (var context = new DatabaseContext())
{
    var query = context.Table.AsQueryable();
    var result = query.Where(o => o.Id == param).ToList();
}

此查询大约需要10秒钟.

using (var context = new DatabaseContext())
{
    var query = context.Table.AsQueryable();
    var result = query.Where(o => o.Id == 123456).ToList();
}

此查询不到1秒.

我刚刚发现EntityFramework会生成两个不同的查询.

查询1:

SELECT TOP (20) 
[Project1].[Id] AS [Id], 
[Project1].[Name] AS [Name],  
FROM ( SELECT [Project1].[Id] AS [Id], [Project1].[Name] AS [Name], row_number() OVER (ORDER BY [Project1].[Id] DESC) AS [row_number]
    FROM ( SELECT 
        [Extent1].[Id] AS [Id], 
        [Extent1].[Name] AS [Name]
        FROM [dbo].[Table] AS [Extent1]
        WHERE [Extent1].[Id] = @p__linq__0
    )  AS [Project1]
)  AS [Project1]
WHERE [Project1].[row_number] > 0
ORDER BY [Project1].[Id] DESC
-- p__linq__0: '2932323' (Type = Int32, IsNullable = false)

查询2:

SELECT TOP (20) 
[Filter1].[Id] AS [Id], 
[Filter1].[Name] AS [Name]
FROM ( SELECT [Extent1].[Id] AS [Id], [Extent1].[Name] AS [Name], row_number() OVER (ORDER BY [Extent1].[Id] DESC) AS [row_number]
    FROM [dbo].[Table] AS [Extent1]
    WHERE 2932323 = [Extent1].[Id]
)  AS [Filter1]
WHERE [Filter1].[row_number] > 0
ORDER BY [Filter1].[Id] DESC

有没有办法加快第一种或另一种方式来做到这一点？

Answer 1

恕我直言，看到了 sql 查询，这不仅仅是 EF 相关的性能问题，而是 SQL Server 性能问题。

您应该考虑以下事项：

• 由于 Id 不是 PK：在其上创建索引；
• 用于EXEC sp_updatestats更新统计信息并帮助数据库服务器产生更好的执行计划。

顺便说一句：SSMS 中的查询 1 需要多长时间？