实体框架在每次编译后首次加载都很慢 [英] Entity framework very slow to load for first time after every compilation

问题描述

标题显示我使用实体框架对SQL Server数据库进行第一次查询时遇到问题。我已经尝试寻找答案，但没有人似乎实际上有一个解决方案。

测试是在Visual Studio 2012中使用实体框架6完成的，我也使用T4视图模板预编译视图。数据库位于SQL Server 2008上。我们有大约400个POCO（400个映射文件），数据库表中只有100行数据。

以下捕获是我的测试代码和结果。

  static void Main（string [] args）{
 Stopwatch st = new Stopwatch（）; 
 st.Start（）; 
 new TestDbContext（）。Set< Table1> .FirstOrDefault（）; 
 st.stop（）; 
 Console.WriteLine（First Time+ st.ElapsedMilliseconds +milliseconds）; 
 
 st.Reset（）; 
 st.Start（）; 
 new TestDbContext（）。Set< Table1> .FirstOrDefault（）; 
 st.stop（）; 
 Console.WriteLine（Second Time+ st.ElapsedMilliseconds +milliseconds）; 
} 
  

测试结果

 首次15480毫秒
第二次10毫秒
  

解决方案

在第一个查询EF中编译模型。这可能需要一些严重的时间，一个这样大的模型。

以下是3条建议： http://www.fusonic.net/en/blog/2014/07/09/three-steps-for-fast-entityframework- 6.1-first-query-performance /

总结：

1. 使用缓存的数据库模型存储


2. 生成预编译视图


3. 使用n-gen生成实体框架的预编译版本，以避免错误

我还会确保在执行基准测试时在发布模式下编译应用程序。

另一个解决方案是分析DBContext。 400个实体是很多的，应该比较好的使用较小的块。我没有尝试过，但我认为可以逐个构建模型，这意味着没有一个负载需要15秒。参见Julie Lerman的这篇文章 https://msdn.microsoft.com/en-us /magazine/jj883952.aspx

As the title suggest i'm having a problem with the first query against a SQL Server database using the Entity Framework. I have tried looking for an answer but no one seems to actually have a solution to this.

The tests was done in Visual Studio 2012 using Entity Framework 6, I also used the T4 views template to pre-compile the views. The database was on a SQL Server 2008. We have about 400 POCOs (400 mapping files), only have 100 rows data in database table.

Following capture is my test code and result.

static void Main(string[] args){
    Stopwatch st=new Stopwatch();
    st.Start();
    new TestDbContext().Set<Table1>.FirstOrDefault();
    st.stop();
    Console.WriteLine("First Time "+st.ElapsedMilliseconds+ " milliseconds");

    st.Reset();
    st.Start();
    new TestDbContext().Set<Table1>.FirstOrDefault();
    st.stop();
    Console.WriteLine("Second Time "+st.ElapsedMilliseconds+ " milliseconds");
}

Test results

First Time 15480 milliseconds
Second Time 10 milliseconds

解决方案

On the first query EF compiles the model. This can take some serious time for a model this large.

Here is 3 suggestions: http://www.fusonic.net/en/blog/2014/07/09/three-steps-for-fast-entityframework-6.1-first-query-performance/

A summary:

1. Using a cached db model store
2. Generate pre-compiled views
3. Generate pre-compiled version of entityframework using n-gen to avoid jitting

I would also make sure that I compile the application in release mode when doing the benchmarks.

Another solution is to look at splitting the DBContext. 400 entities is a lot and it should be nicer to work with smaller chunks. I haven't tried it but I assume it would be possible to build the models one by one meaning no single load takes 15s. See this post by Julie Lerman https://msdn.microsoft.com/en-us/magazine/jj883952.aspx

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