一个Entity Framework Core的性能优化案例

概要

本文提供一个EF Core的优化案例，主要介绍一些EF Core常用的优化方法，以及在优化过程中，出现性能反复的时候的解决方法，并澄清一些对优化概念的误解，例如AsNoTracking并不包治百病。

本文使用的是Dotnet 6.0和EF Core 7.0。

代码及实现

背景介绍

本文主要使用一个图书和作者的案例，用于介绍优化过程。

  • 一个作者Author有多本自己写的的图书Book
  • 一本图书Book有一个发行商Publisher
  • 一个作者Author是一个系统用户User
  • 一个系统用户User有多个角色Role

本实例中Author表和Book数据量较大，记录数量全部过万条，其它数据表记录大概都是几十或几百条。具体实体类定义请见附录。

查询需求

我们需要查找写书最多的前两名作家，该作家需要年龄在20岁以上，国籍是法国。需要他们的FirstName， LastName， Email，UserName以及在1900年以前他们发行的图书信息，包括书名Name和发行日期Published。

基本优化思路

本人做EF Core的复杂查询优化，并不推荐直接查看生成的SQL代码，我习惯按照如下方式进行：

首先，进行EF的LINQ代码检查（初筛），找到明显的错误。

  1. 查看代码中是否有基本错误，主要针对全表载入的问题。例如EF需要每一步的LINQ扩展方法的返回值都是IQueryable类型，不能有IEnumerable类型；
  2. 查看是否有不需要的栏位；
  3. 根据情况决定是否加AsNoTracking，注意这个东西有时候加了也没用；

其次，找到数据量较大的表，进行代码整理和针对大数据表的优化（精细化调整）

  1. 在操作大数据表时候，先要进行基本的过滤；
  2. 投影操作Select应该放到排序操作后面；
  3. 减少返回值数量，推荐进行分页操作；

本人推荐一旦出现性能反复的时候或者代码整体基本完成的时候，再去查看生成的SQL代码。

初始查询代码

public  List<AuthorWeb> GetAuthors() {using var dbContext = new AppDbContext();var authors = dbContext.Authors.Include(x => x.User).ThenInclude(x => x.UserRoles).ThenInclude(x => x.Role).Include(x => x.Books).ThenInclude(x => x.Publisher).ToList().Select(x => new AuthorWeb{UserCreated = x.User.Created,UserEmailConfirmed = x.User.EmailConfirmed,UserFirstName = x.User.FirstName,UserLastActivity = x.User.LastActivity,UserLastName = x.User.LastName,UserEmail = x.User.Email,UserName = x.User.UserName,UserId = x.User.Id,RoleId = x.User.UserRoles.FirstOrDefault(y => y.UserId == x.UserId).RoleId,BooksCount = x.BooksCount,AllBooks = x.Books.Select(y => new BookWeb{Id = y.Id,Name = y.Name,Published = y.Published,ISBN = y.ISBN,PublisherName = y.Publisher.Name}).ToList(),AuthorAge = x.Age,AuthorCountry = x.Country,AuthorNickName = x.NickName,Id = x.Id}).ToList().Where(x => x.AuthorCountry == "France" && x.AuthorAge == 20).ToList();var orderedAuthors = authors.OrderByDescending(x => x.BooksCount).ToList().Take(2).ToList();List<AuthorWeb> finalAuthors = new List<AuthorWeb>();foreach (var author in orderedAuthors){List<BookWeb> books = new List<BookWeb>();var allBooks = author.AllBooks;foreach (var book in allBooks){if (book.Published.Year < 1900){book.PublishedYear = book.Published.Year;books.Add(book);}}author.AllBooks = books;finalAuthors.Add(author);}return finalAuthors;}

Benchmark测试后，系统资源使用情况如下：

在这里插入图片描述

代码性能非常差，内存消耗很大，一次执行就要消耗190MB，执行时间超过2s。如果是放到WebAPI里面调用，用户会有明显的卡顿感觉；如果面临高并发的情况，很可得会造成服务器资源紧张，返回各种500错误。

优化代码

初筛

按照我们的优化思路，在查看上面的代码后，发现一个严重的问题。

虽然每次LINQ查询返回都是IQueryable类型，但是源码中有多个ToList()，尤其是第一个，它的意思是将Author， Book，User，Role，Publisher等多个数据表的数据全部载入，前面已经说了，Author， Book两张表的数据量很大，必然影响性能。

我们需要删除前面多余的ToList()，只保留最后的即可。请参考附录中的方法GetAuthors_RemoveToList()。

在GetAuthors_RemoveToList()基础上，对照用户的需求，发现查询结果中包含了Role相关的信息和很多Id信息，但是查询结果并不需要这些，因此必须删掉。请参考附录中的方法GetAuthorsOptimized_RemoveColumn()

在GetAuthorsOptimized_RemoveColumn的基础上，我们再加入AsNoTracking方法。请参考附录中的方法GetAuthorsOptimized_AsNoTracking()

我们在Benchmark中，测试上面提到的三个方法，直接结果如下：

在这里插入图片描述

从Benchmark的测试结果上看，删除多余ToList方法和删除多余的栏位，确实带来了性能的大幅提升。

但是增加AsNoTracking，性能提反而下降了一点。这也说明了AsNoTracking并不是适用所有场景。Select投影操作生成的AuthorWeb对像，并不是EF管理的，与DbContext无关，它只是作为前端API的返回值。相当于EF做了没有用的事，所以性能略有下降。

代码进一步调整

初筛阶段完成后，下面对代码进一步整理

下面Take和Order操作可以并入基本的查询中，Take可以帮助我们减少返回值的数量。请见 GetAuthorsOptimized_ChangeOrder()方法。

var orderedAuthors = authors.OrderByDescending(x => x.BooksCount).ToList().Take(2).ToList();

在GetAuthorsOptimized_ChangeOrder基础上，对于dbContext.Authors，Author是一张数据量很大的表，我们需要在其进行联表操作前，先过滤掉不需要的内容，所以我们可以把Where前提，还有就是将排序操作放到投影的Select前面完成。请见 GetAuthorsOptimized_ChangeOrder方法。

上面的两个优化方法的执行结果如下：

在这里插入图片描述
可以看到性略能有提升。

下面我们为了进一步提升性能，可以查看一下生成的SQL代码，看看是否还有优化的空间。

GetAuthorsOptimized_ChangeOrder方法生成的SQL如下：

      SELECT [u].[FirstName], [u].[LastName], [u].[Email], [u].[UserName], [t].[
BooksCount], [t].[Id], [u].[Id], [b].[Name], [b].[Published], [b].[Id], [t].[Age
], [t].[Country]FROM (SELECT TOP(@__p_0) [a].[Id], [a].[Age], [a].[BooksCount], [a].[Country
], [a].[UserId]FROM [Authors] AS [a]WHERE [a].[Country] = N'France' AND [a].[Age] >= 20ORDER BY [a].[BooksCount] DESC) AS [t]INNER JOIN [Users] AS [u] ON [t].[UserId] = [u].[Id]LEFT JOIN [Books] AS [b] ON [t].[Id] = [b].[AuthorId]ORDER BY [t].[BooksCount] DESC, [t].[Id], [u].[Id]

从生成SQL来看，Author表在使用之前过滤掉了相关的内容，但是直接Left Join了[Books]这个大表。我们可以按照前面提到的1900年以前的查询要求，在左联之前先过滤一下，请参考 GetAuthorsOptimized_SelectFilter方法。

该方法执行后，生成的SQL如下：

      SELECT [u].[FirstName], [u].[LastName], [u].[Email], [u].[UserName], [t].[
BooksCount], [t].[Id], [u].[Id], [t0].[Name], [t0].[Published], [t0].[Id], [t].[
Age], [t].[Country]FROM (SELECT TOP(@__p_1) [a].[Id], [a].[Age], [a].[BooksCount], [a].[Country
], [a].[UserId]FROM [Authors] AS [a]WHERE [a].[Country] = N'France' AND [a].[Age] >= 20ORDER BY [a].[BooksCount] DESC) AS [t]INNER JOIN [Users] AS [u] ON [t].[UserId] = [u].[Id]LEFT JOIN (SELECT [b].[Name], [b].[Published], [b].[Id], [b].[AuthorId]FROM [Books] AS [b]WHERE [b].[Published] < @__date_0) AS [t0] ON [t].[Id] = [t0].[AuthorId]ORDER BY [t].[BooksCount] DESC, [t].[Id], [u].[Id]

在左联之前，确实进行了过滤，该方法的性能测试如下：

在这里插入图片描述
在避免Book表直接进行左联后，性能有所提升。

最后一个优化点，是在EF Core 5.0里面提供了带Filter功能的Include方法，也可以用于本案例的优化，但是该特性但是存在一些局限性，具体请参考EF Core中带过滤器参数的Include方法

但是此方法又涉及了将IQueryable转换成IEnumerable的操作，最后要将生成的Author对象全部转换成AuthorWeb对象。代码过于繁琐，而且带来的性能提升也不明显。因此放弃这个点。

dbContext.Authors.AsNoTracking().Include(x => x.Books.Where(b => b.Published < date))......

结论

从这个优化过程来看，其实对性能提升最大的贡献就是删除多余的ToList()，避免全表载入和删除不需要的栏位两项。其它所谓更精细的优化，性能提升有限。

附录

实体类定义

 public class Author{public int Id { get; set; }public int Age { get; set; }public string Country { get; set; }public int BooksCount { get; set; }public string NickName { get; set; }[ForeignKey("UserId")]public User User { get; set; }public int UserId { get; set; }public virtual List<Book> Books { get; set; } = new List<Book>();}public class Book{public int Id { get; set; }public string Name { get; set; }[ForeignKey("AuthorId")]public Author Author { get; set; }public int AuthorId { get; set; }public DateTime Published { get; set; }public string ISBN { get; set; }[ForeignKey("PublisherId")]public Publisher Publisher { get; set; }public int PublisherId { get; set; }}
public class Publisher{public int Id { get; set; }public string Name { get; set; }public DateTime Established { get; set; }}public class User{public int Id { get; set; }public string FirstName { get; set; }public string LastName { get; set; }public string UserName { get; set; }public string Email { get; set; }public virtual List<UserRole> UserRoles { get; set; } = new List<UserRole>();public DateTime Created { get; set; }public bool EmailConfirmed { get; set; }public DateTime LastActivity { get; set; }}public class Role{public int Id { get; set; }public virtual List<UserRole> UserRoles { get; set; } = new List<UserRole>();public string Name { get; set; }}public  class AuthorWeb{public DateTime UserCreated { get; set; }public bool UserEmailConfirmed { get; set; }public string UserFirstName { get; set; }public DateTime UserLastActivity { get; set; }public string UserLastName { get; set; }public string UserEmail { get; set; }public string UserName { get; set; }public int UserId { get; set; }public int AuthorId { get; set; }public int Id { get; set; }public int RoleId { get; set; }public int BooksCount { get; set; }public List<BookWeb> AllBooks { get; set; }public int AuthorAge { get; set; }public string AuthorCountry { get; set; }public string AuthorNickName { get; set; }}public class BookWeb{public int Id { get; set; }public string Name { get; set; }public DateTime Published { get; set; }public int PublishedYear { get; set; }public string PublisherName { get; set; }public string ISBN { get; set; }}

优化方法

[Benchmark]
public  List<AuthorWeb> GetAuthors() {using var dbContext = new AppDbContext();var authors = dbContext.Authors.Include(x => x.User).ThenInclude(x => x.UserRoles).ThenInclude(x => x.Role).Include(x => x.Books).ThenInclude(x => x.Publisher).ToList().Select(x => new AuthorWeb{UserCreated = x.User.Created,UserEmailConfirmed = x.User.EmailConfirmed,UserFirstName = x.User.FirstName,UserLastActivity = x.User.LastActivity,UserLastName = x.User.LastName,UserEmail = x.User.Email,UserName = x.User.UserName,UserId = x.User.Id,RoleId = x.User.UserRoles.FirstOrDefault(y => y.UserId == x.UserId).RoleId,BooksCount = x.BooksCount,AllBooks = x.Books.Select(y => new BookWeb{Id = y.Id,Name = y.Name,Published = y.Published,ISBN = y.ISBN,PublisherName = y.Publisher.Name}).ToList(),AuthorAge = x.Age,AuthorCountry = x.Country,AuthorNickName = x.NickName,Id = x.Id}).ToList().Where(x => x.AuthorCountry == "France" && x.AuthorAge >= 20).ToList();var orderedAuthors = authors.OrderByDescending(x => x.BooksCount).ToList().Take(2).ToList();List<AuthorWeb> finalAuthors = new List<AuthorWeb>();foreach (var author in orderedAuthors){List<BookWeb> books = new List<BookWeb>();var allBooks = author.AllBooks;foreach (var book in allBooks){if (book.Published.Year < 1900){book.PublishedYear = book.Published.Year;books.Add(book);}}author.AllBooks = books;finalAuthors.Add(author);}return finalAuthors;}[Benchmark]public List<AuthorWeb> GetAuthors_RemoveToList(){using var dbContext = new AppDbContext();var authors = dbContext.Authors.Include(x => x.User).ThenInclude(x => x.UserRoles).ThenInclude(x => x.Role).Include(x => x.Books).ThenInclude(x => x.Publisher)//  .ToList().Select(x => new AuthorWeb{UserCreated = x.User.Created,UserEmailConfirmed = x.User.EmailConfirmed,UserFirstName = x.User.FirstName,UserLastActivity = x.User.LastActivity,UserLastName = x.User.LastName,UserEmail = x.User.Email,UserName = x.User.UserName,UserId = x.User.Id,RoleId = x.User.UserRoles.FirstOrDefault(y => y.UserId == x.UserId).RoleId,BooksCount = x.BooksCount,AllBooks = x.Books.Select(y => new BookWeb{Id = y.Id,Name = y.Name,Published = y.Published,ISBN = y.ISBN,PublisherName = y.Publisher.Name}).ToList(),AuthorAge = x.Age,AuthorCountry = x.Country,AuthorNickName = x.NickName,Id = x.Id})// .ToList().Where(x => x.AuthorCountry == "France" && x.AuthorAge >=20).ToList();var orderedAuthors = authors.OrderByDescending(x => x.BooksCount).ToList().Take(2).ToList();List<AuthorWeb> finalAuthors = new List<AuthorWeb>();foreach (var author in orderedAuthors){List<BookWeb> books = new List<BookWeb>();var allBooks = author.AllBooks;foreach (var book in allBooks){if (book.Published.Year < 1900){book.PublishedYear = book.Published.Year;books.Add(book);}}author.AllBooks = books;finalAuthors.Add(author);}return finalAuthors;}[Benchmark]public  List<AuthorWeb> GetAuthorsOptimized_RemoveColumn(){using var dbContext = new AppDbContext();var authors = dbContext.Authors//   .Include(x => x.User)//.ThenInclude(x => x.UserRoles)//   .ThenInclude(x => x.Role)//   .Include(x => x.Books)//     .ThenInclude(x => x.Publisher).Select(x => new AuthorWeb{//   UserCreated = x.User.Created,//  UserEmailConfirmed = x.User.EmailConfirmed,UserFirstName = x.User.FirstName,//   UserLastActivity = x.User.LastActivity,UserLastName = x.User.LastName,UserEmail = x.User.Email,UserName = x.User.UserName,//     UserId = x.User.Id,//     RoleId = x.User.UserRoles.FirstOrDefault(y => y.UserId == x.UserId).RoleId,BooksCount = x.BooksCount,AllBooks = x.Books.Select(y => new BookWeb{//    Id = y.Id,Name = y.Name,Published = y.Published,//       ISBN = y.ISBN,//         PublisherName = y.Publisher.Name}).ToList(),AuthorAge = x.Age,AuthorCountry = x.Country,AuthorNickName = x.NickName,//   Id = x.Id}).Where(x => x.AuthorCountry == "France" && x.AuthorAge >=20).ToList();var orderedAuthors = authors.OrderByDescending(x => x.BooksCount).ToList().Take(2).ToList();List<AuthorWeb> finalAuthors = new List<AuthorWeb>();foreach (var author in orderedAuthors){List<BookWeb> books = new List<BookWeb>();var allBooks = author.AllBooks;foreach (var book in allBooks){if (book.Published.Year < 1900){book.PublishedYear = book.Published.Year;books.Add(book);}}author.AllBooks = books;finalAuthors.Add(author);}return finalAuthors;}[Benchmark]public List<AuthorWeb> GetAuthorsOptimized_AsNoTracking(){using var dbContext = new AppDbContext();var authors = dbContext.Authors.AsNoTracking()// .Include(x => x.User)//   .ThenInclude(x => x.UserRoles)//   .ThenInclude(x => x.Role)//    .Include(x => x.Books)//   .ThenInclude(x => x.Publisher).Select(x => new AuthorWeb{//UserCreated = x.User.Created,//    UserEmailConfirmed = x.User.EmailConfirmed,UserFirstName = x.User.FirstName,// UserLastActivity = x.User.LastActivity,UserLastName = x.User.LastName,UserEmail = x.User.Email,UserName = x.User.UserName,//  UserId = x.User.Id,//RoleId = x.User.UserRoles.FirstOrDefault(y => y.UserId == x.UserId).RoleId,BooksCount = x.BooksCount,AllBooks = x.Books.Select(y => new BookWeb{// Id = y.Id,Name = y.Name,Published = y.Published,//ISBN = y.ISBN,//PublisherName = y.Publisher.Name}).ToList(),AuthorAge = x.Age,AuthorCountry = x.Country,//AuthorNickName = x.NickName,Id = x.Id}).Where(x => x.AuthorCountry == "France" && x.AuthorAge >=20).ToList();var orderedAuthors = authors.OrderByDescending(x => x.BooksCount).ToList().ToList();List<AuthorWeb> finalAuthors = new List<AuthorWeb>();foreach (var author in authors){List<BookWeb> books = new List<BookWeb>();var allBooks = author.AllBooks;foreach (var book in allBooks){if (book.Published.Year < 1900){book.PublishedYear = book.Published.Year;books.Add(book);}}author.AllBooks = books;finalAuthors.Add(author);}return finalAuthors;}[Benchmark]public List<AuthorWeb> GetAuthorsOptimized_Take_Order(){using var dbContext = new AppDbContext();var authors = dbContext.Authors.AsNoTracking().Select(x => new AuthorWeb{UserFirstName = x.User.FirstName,UserLastName = x.User.LastName,UserEmail = x.User.Email,UserName = x.User.UserName,BooksCount = x.BooksCount,AllBooks = x.Books.Select(y => new BookWeb{Name = y.Name,Published = y.Published,}).ToList(),AuthorAge = x.Age,AuthorCountry = x.Country,AuthorNickName = x.NickName,}).Where(x => x.AuthorCountry == "France" && x.AuthorAge >=20).OrderByDescending(x => x.BooksCount).Take(2).ToList();// var orderedAuthors = authors.OrderByDescending(x => x.BooksCount).ToList().ToList();List<AuthorWeb> finalAuthors = new List<AuthorWeb>();foreach (var author in authors){List<BookWeb> books = new List<BookWeb>();var allBooks = author.AllBooks;foreach (var book in allBooks){if (book.Published.Year < 1900){book.PublishedYear = book.Published.Year;books.Add(book);}}author.AllBooks = books;finalAuthors.Add(author);}return finalAuthors;}[Benchmark]public List<AuthorWeb> GetAuthorsOptimized_ChangeOrder(){using var dbContext = new AppDbContext();var authors = dbContext.Authors.AsNoTracking().Where(x => x.Country == "France" && x.Age >=20).OrderByDescending(x => x.BooksCount)// .Include(x => x.User)//   .ThenInclude(x => x.UserRoles)//   .ThenInclude(x => x.Role)//    .Include(x => x.Books)//   .ThenInclude(x => x.Publisher).Select(x => new AuthorWeb{//UserCreated = x.User.Created,//    UserEmailConfirmed = x.User.EmailConfirmed,UserFirstName = x.User.FirstName,// UserLastActivity = x.User.LastActivity,UserLastName = x.User.LastName,UserEmail = x.User.Email,UserName = x.User.UserName,//  UserId = x.User.Id,//RoleId = x.User.UserRoles.FirstOrDefault(y => y.UserId == x.UserId).RoleId,BooksCount = x.BooksCount,AllBooks = x.Books.Select(y => new BookWeb{// Id = y.Id,Name = y.Name,Published = y.Published,//ISBN = y.ISBN,//PublisherName = y.Publisher.Name}).ToList(),AuthorAge = x.Age,AuthorCountry = x.Country,//AuthorNickName = x.NickName,Id = x.Id})                                     .Take(2).ToList();// var orderedAuthors = authors.OrderByDescending(x => x.BooksCount).ToList().ToList();List<AuthorWeb> finalAuthors = new List<AuthorWeb>();foreach (var author in authors){List<BookWeb> books = new List<BookWeb>();var allBooks = author.AllBooks;foreach (var book in allBooks){if (book.Published.Year < 1900){book.PublishedYear = book.Published.Year;books.Add(book);}}author.AllBooks = books;finalAuthors.Add(author);}return finalAuthors;}//  [Benchmark]public List<AuthorWeb> GetAuthorsOptimized_IncludeFilter(){using var dbContext = new AppDbContext();var date = new DateTime(1900, 1, 1);var authors = dbContext.Authors.AsNoTracking().Include(x => x.Books.Where(b => b.Published < date)).Include(x => x.User)// .IncludeFilter(x =>x.Books.Where(b =>b.Published.Year < 1900)).Where(x => x.Country == "France" && x.Age >=20).OrderByDescending(x => x.BooksCount)//   .ThenInclude(x => x.UserRoles)//   .ThenInclude(x => x.Role)//    .Include(x => x.Books)//   .ThenInclude(x => x.Publisher).Take(2).ToList();// var orderedAuthors = authors.OrderByDescending(x => x.BooksCount).ToList().ToList();var authorList = authors.AsEnumerable().Select(x => new AuthorWeb{//UserCreated = x.User.Created,//    UserEmailConfirmed = x.User.EmailConfirmed,UserFirstName = x.User.FirstName,// UserLastActivity = x.User.LastActivity,UserLastName = x.User.LastName,UserEmail = x.User.Email,UserName = x.User.UserName,//  UserId = x.User.Id,//RoleId = x.User.UserRoles.FirstOrDefault(y => y.UserId == x.UserId).RoleId,BooksCount = x.BooksCount,AllBooks = x.Books//    .Where(b => b.Published < date).Select(y => new BookWeb{// Id = y.Id,Name = y.Name,Published = y.Published,//ISBN = y.ISBN,//PublisherName = y.Publisher.Name}).ToList(),AuthorAge = x.Age,AuthorCountry = x.Country,//AuthorNickName = x.NickName,//    Id = x.Id}).ToList();return authorList;}[Benchmark]public List<AuthorWeb> GetAuthorsOptimized_SelectFilter(){using var dbContext = new AppDbContext();var date = new DateTime(1900, 1, 1);var authors = dbContext.Authors.AsNoTracking().Include(x => x.Books.Where(b => b.Published < date)).Where(x => x.Country == "France" && x.Age >=20).OrderByDescending(x => x.BooksCount).Select(x => new AuthorWeb{//UserCreated = x.User.Created,//    UserEmailConfirmed = x.User.EmailConfirmed,UserFirstName = x.User.FirstName,// UserLastActivity = x.User.LastActivity,UserLastName = x.User.LastName,UserEmail = x.User.Email,UserName = x.User.UserName,//  UserId = x.User.Id,//RoleId = x.User.UserRoles.FirstOrDefault(y => y.UserId == x.UserId).RoleId,BooksCount = x.BooksCount,AllBooks = x.Books.Where(b => b.Published < date).Select(y => new BookWeb{// Id = y.Id,Name = y.Name,Published = y.Published,//ISBN = y.ISBN,//PublisherName = y.Publisher.Name}).ToList(),AuthorAge = x.Age,AuthorCountry = x.Country,//AuthorNickName = x.NickName,//    Id = x.Id}).Take(2).ToList();return authors;}

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