实体框架核心的性能 [英] Performance of Entity Framework Core

问题描述

我对EF Core非常陌生.我一直使用EF 6.0，而不必使用包含.现在问题来了，我应该如何处理这些包括在内的问题.我想出了三个可能的选择，想知道您最想使用/哪个是最快的，为什么?

I'm quite new to the EF Core. I always used the EF 6.0 and never had to use an include. Now the question comes up how i should work with these includes. I figured out three possible options and wanted to know wich would you prefer to use/which is the fastest and why?

在这些样本中，我的目的是获取俱乐部的详细信息.我想检查一个具有相应ID的俱乐部是否存在，然后获取全部信息.

In these samples my intention is to get the details of a club. I want to check if a club with the corresponding id exists and then get the whole information.

选项1:

using (var context = new TrainingSchedulerContext())
{
    var clubs = context.Clubs.Where(c => c.Id == clubId);
    if (clubs.Count() == 0)
        return NotFound();

    var club = clubs.Include(c => c.Memberships)
        .Include(c => c.MembershipRequests)
        .Include(c => c.TrainingTimes)
        .Include(c => c.AdminRoles)
        .SingleOrDefault();
}

选项2:

using (var context = new TrainingSchedulerContext())
{
    var club = context.Clubs.Include(c => c.Memberships)
            .Include(c => c.MembershipRequests)
            .Include(c => c.TrainingTimes)
            .Include(c => c.AdminRoles)
            .SingleOrDefault(c => c.Id == clubId);

    if (club == null)
        return NotFound();
}

选项3:

using (var context = new TrainingSchedulerContext())
{
    var club = context.Clubs.SingleOrDefault(c => c.Id == clubId);
    if (club == null)
        return NotFound();

    club = context.Clubs.Include(c => c.Memberships)
        .Include(c => c.MembershipRequests)
        .Include(c => c.TrainingTimes)
        .Include(c => c.AdminRoles)
        .SingleOrDefault(c => c.Id == clubId);
}

推荐答案

让我们从最坏到最好:

• 选项3 :这显然是最糟糕的.您正在将整个项目下载到内存中，只是为了扔掉它.这是浪费资源.
• 选项1 :这不是最佳方法，因为您正在对数据库执行2个查询，一个查询用于Count，另一个查询用于SingleOrDefault.不需要第一个，因此:
• 选项2 :这是最好的情况，因为如果该项目不存在，则不会从数据库下载任何内容，因此您不必为此担心，它也是一个数据库调用.

• Option 3: this is obviously the worst. You are downloading the entire item into memory just for throwing it away. This is a waste of resources.
• Option 1: this is not the best way because you are executing 2 queries against the database, one for Count and another one for SingleOrDefault. The first one is not needed, hence:
• Option 2: this is the best case because if the item does not exist, nothing will be downloaded from the database, so you don't have to worry about that, and it's also a single database call.

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