blocks|key|800711|text|在第一个查询中，EF编译模型。对于这么大的模型来说，这可能需要一些严肃的时间。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|800712|这里有三个建议：http://www.fusonic.net/en/blog/2014/07/09/three-steps-for-fast-entityframework-6.1-first-query-performance/|offset|length|800713|摘要：|800714|使用缓存的db模型存储|ordered-list-item|800715|生成预编译视图。|800716|使用n-gen生成实体框架的预编译版本，以避免跳转。|800717|我还将确保在执行基准测试时，以发布模式编译应用程序。|800718|另一个解决方案是考虑拆分DBContext。400个实体非常多，与较小的块一起工作应该更好。我还没有试过，但我认为可以一个接一个地构建模型，这意味着没有单一的负载需要15s。参见朱莉·勒曼https://msdn.microsoft.com/en-us/magazine/jj883952.aspx撰写的这篇文章|800719|entityMap|0|LINK|mutability|MUTABLE|url|http://www.fusonic.net/en/blog/2014/07/09/three-steps-for-fast-entityframework-6.1-first-query-performance/|1|https://msdn.microsoft.com/en-us/magazine/jj883952.aspx^0|0|8|2Z|0|0|0|0|0|0|0|2M|1J|1|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@]|9|@$D|14|E|15|1|16]]|A|$]]|$1|F|3|G|5|6|7|17|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|18|8|@]|9|@]|A|$]]|$1|K|3|L|5|J|7|19|8|@]|9|@]|A|$]]|$1|M|3|N|5|J|7|1A|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1B|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1C|8|@]|9|@$D|1D|E|1E|1|1F]]|A|$]]|$1|S|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]|10|$5|V|W|X|A|$Y|11]]]]

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

Here are 3 suggestions: <a href="http://www.fusonic.net/en/blog/2014/07/09/three-steps-for-fast-entityframework-6.1-first-query-performance/" rel="noreferrer">http://www.fusonic.net/en/blog/2014/07/09/three-steps-for-fast-entityframework-6.1-first-query-performance/</a>

A summary:

<ol>
<li>Using a cached db model store</li>
<li>Generate pre-compiled views</li>
<li>Generate pre-compiled version of entityframework using n-gen to avoid jitting </li>
</ol>

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 <a href="https://msdn.microsoft.com/en-us/magazine/jj883952.aspx" rel="noreferrer">https://msdn.microsoft.com/en-us/magazine/jj883952.aspx</a>

blocks|key|745469|text|我认为这不是一个很好的解决办法。Ado.net看起来性能要好得多。不过，这是我的意见。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|745470|或者看看他们。|745471|https://msdn.microsoft.com/tr-tr/data/dn582034|offset|length|745472|https://msdn.microsoft.com/en-us/library/cc853327(v=vs.100).aspx|745473|entityMap|0|LINK|mutability|MUTABLE|url|1^0|0|0|0|1A|0|0|0|1S|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@$F|U|G|V|1|W]]|A|$]]|$1|H|3|I|5|6|7|X|8|@]|9|@$F|Y|G|Z|1|10]]|A|$]]|$1|J|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|E]]|Q|$5|M|N|O|A|$P|I]]]]

I think that is not a very good solution. Ado.net looks like a lot more performance. However, this is my opinion.

Alternatively look at them.

<a href="https://msdn.microsoft.com/tr-tr/data/dn582034" rel="nofollow noreferrer">https://msdn.microsoft.com/tr-tr/data/dn582034</a>

<a href="https://msdn.microsoft.com/en-us/library/cc853327(v=vs.100).aspx" rel="nofollow noreferrer">https://msdn.microsoft.com/en-us/library/cc853327(v=vs.100).aspx</a>

blocks|key|745475|text|这是我的工作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|745476|using+(MyEntities+db+=+new+MyEntities())++++++++++++++++
{
+++db.Configuration.AutoDetectChangesEnabled+=+false;+//+<-----+trick
+++db.Configuration.LazyLoadingEnabled+=+false;+//+<-----+trick

+++DateTime+Created+=+DateTime.Now;

+++var+obj+=+from+tbl+in+db.MyTable
++++++where+DateTime.Compare(tbl.Created,+Created)+==+0
++++++select+tbl;

+++dataGrid1.ItemsSource+=+obj.ToList();
+++dataGrid.Items.Refresh();
}|code-block|syntax|javascript|745477|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

this work for me:

<pre><code>using (MyEntities db = new MyEntities()) 
{
 db.Configuration.AutoDetectChangesEnabled = false; // &lt;----- trick
 db.Configuration.LazyLoadingEnabled = false; // &lt;----- trick

 DateTime Created = DateTime.Now;

 var obj = from tbl in db.MyTable
 where DateTime.Compare(tbl.Created, Created) == 0
 select tbl;

 dataGrid1.ItemsSource = obj.ToList();
 dataGrid.Items.Refresh();
}
</code></pre>

blocks|key|1355231|text|你可以试试这样的方法：(这对我有用)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1355232|protected+void+Application_Start()
{

++++Start(()+=>
++++{
++++++++using+(EF.DMEntities+context+=+new+EF.DMEntities())
++++++++{
++++++++++++context.DMUsers.FirstOrDefault();
++++++++}
++++});
}
private+void+Start(Action+a)
{
++++a.BeginInvoke(null,+null);
}+|code-block|syntax|javascript|1355233|Entity+Framework+-+First+query+slow|offset|length|1355234|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/3891125/entity-framework-first-query-slow^0|0|0|0|Z|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

You can try something like this: (it worked for me)

<pre><code>protected void Application_Start()
{

 Start(() =&gt;
 {
 using (EF.DMEntities context = new EF.DMEntities())
 {
 context.DMUsers.FirstOrDefault();
 }
 });
}
private void Start(Action a)
{
 a.BeginInvoke(null, null);
} 
</code></pre>

<a href="https://stackoverflow.com/questions/3891125/entity-framework-first-query-slow">Entity Framework - First query slow</a>

blocks|key|800791|text|使用EF，您可以在调用services.AddDbContext后早期欺骗和加载模型(您可能也可以使用EF6进行类似的操作，但我还没有对其进行测试)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|800792|services.AddDbContext<MyDbContext>(options+=>+...);
var+options+=+services.BuildServiceProvider()
++++++++++++++++++++++.GetRequiredService<DbContextOptions<MyDbContext>>();
Task.Run(()+=>
{
++++using(var+dbContext+=+new+MyDbContext(options))
++++{
++++++++var+model+=+dbContext.Model;+//force+the+model+creation
++++}
});|code-block|syntax|javascript|800793|这将在另一个线程中创建dbcontext模型，同时完成应用程序的其余初始化(可能还有其他warmup)和请求的开始。这样，它就会准备得更快。当您需要它时，如果模型尚未完成，EFCore将等待模型的创建。Model是在所有dbcontext实例之间共享的，因此可以触发并忘记这个虚拟DbContext。|800794|entityMap^0|B|L|0|0|2T|5|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

With EF Core, you can cheat and load the model early after you call <code>services.AddDbContext</code> (you can probably do something similar with EF6 too, but I haven't tested it).

<pre><code>services.AddDbContext&lt;MyDbContext&gt;(options =&gt; ...);
var options = services.BuildServiceProvider()
 .GetRequiredService&lt;DbContextOptions&lt;MyDbContext&gt;&gt;();
Task.Run(() =&gt;
{
 using(var dbContext = new MyDbContext(options))
 {
 var model = dbContext.Model; //force the model creation
 }
});
</code></pre>

This will create the model of the dbcontext in another thread while the rest of the initialization of the application is done (and maybe other warmups) and the beginning of a request. This way, it will be ready sooner. When you need it, EFCore will wait for the Model to be created if it hasn't finished already. The <code>Model</code> is shared across all DbContext instances so it is ok to fire and forget this dummy dbcontext.

blocks|key|1354514|text|对我来说，仅在第一个查询中使用AsParallel()就解决了这个问题。这在多个处理器核上运行查询(显然)。我随后的所有查询都没有改变，这只是导致延迟的第一个查询。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1354515|我也尝试了预生成的映射视图https://learn.microsoft.com/en-us/ef/ef6/fundamentals/performance/pre-generated-views，但这并没有大大改善启动时间。|offset|length|1354516|entityMap|0|LINK|mutability|MUTABLE|url|https://learn.microsoft.com/en-us/ef/ef6/fundamentals/performance/pre-generated-views^0|0|D|2D|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

For me, just using AsParallel() in the first query solved the problem. This runs the query on multiple processor cores (apparently). All my subsequent queries are unchanged, it is only the first one which was causing the delay.
I also tried pre-generated mapping views <a href="https://learn.microsoft.com/en-us/ef/ef6/fundamentals/performance/pre-generated-views" rel="nofollow noreferrer">https://learn.microsoft.com/en-us/ef/ef6/fundamentals/performance/pre-generated-views</a> but this did not improve startup time by much.

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.

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

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

Test results

<pre><code>First Time 15480 milliseconds
Second Time 10 milliseconds
</code></pre>

Entity framework very slow to load for first time after every compilation

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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正如标题所示，我在使用实体框架对Server数据库进行第一个查询时遇到了问题。我曾试图寻找答案，但似乎没有人真正有办法解决这个问题。这些测试是在Visual 2012中使用实体框架6完成的，我还使用T4视图模板预编译视图。数据库位于Server 2008上。我们有大约400个POCOs (400个映射文件)，数据库表中...

问实体框架每次编译后第一次加载非常慢
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问实体框架每次编译后第一次加载非常慢EN