如何使用Entity Framework Core创建聚簇索引

时间：2016-08-14 16:18:41

标签： entity-framework entity-framework-core clustered-index

从EF6.1开始，我们可以在属性上指定聚簇索引

public class Person 
{
  [Index(IsClustered = true, IsUnique = true)]
  public long UserName { get; set; }
}

但是这个Index属性现在似乎不在EF Core中？在EF Core中你是如何实现这一目标的？

4 个答案:

答案 0 :(得分：16)

从当前的EF Core文档 - Indexes部分：

  

数据注释

     

无法使用数据注释创建索引。

但是您肯定可以通过Fluent API指定（注意具有chmod 0400 id_rsa前缀的扩展方法似乎表示SqlServer特定的功能）：

In [22]: execute(upload_scripts_data, rps_file) 
[ubuntu@52.90.34.75] Executing task 'upload_scripts_data'
[ubuntu@54.173.57.59] Executing task 'upload_scripts_data'
[ubuntu@54.165.186.168] Executing task 'upload_scripts_data'
!!! Parallel execution exception under host u'ubuntu@54.165.186.168':
Process ubuntu@54.165.186.168:
Traceback (most recent call last):
 File "/home/rerwin21/anaconda2/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
self.run()
 File "/home/rerwin21/anaconda2/lib/python2.7/multiprocessing/process.py", line 114, in run
self._target(*self._args, **self._kwargs)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/tasks.py", line 242, in inner
submit(task.run(*args, **kwargs))
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/tasks.py", line 174, in run
return self.wrapped(*args, **kwargs)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/decorators.py", line 181, in inner
Traceback (most recent call last):

 File "<ipython-input-22-ed18eb00cc62>", line 1, in <module>
execute(upload_scripts_data, rps_file)

 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/tasks.py", line 412, in execute
ran_jobs = jobs.run()

 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/job_queue.py", line 168, in run
self._fill_results(results)

 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/job_queue.py", line 191, in _fill_results
datum = self._comms_queue.get_nowait()

 File "/home/rerwin21/anaconda2/lib/python2.7/multiprocessing/queues.py", line 152, in get_nowait
return self.get(False)

 File "/home/rerwin21/anaconda2/lib/python2.7/multiprocessing/queues.py", line 135, in get
res = self._recv()

TypeError: ('__init__() takes exactly 2 arguments (3 given)', <class 'paramiko.ssh_exception.NoValidConnectionsError'>, (None, 'Unable to connect to port 22 on  or 54.165.186.168'))

  return func(*args, **kwargs)
 File "<ipython-input-19-ed4344124d24>", line 4, in upload_scripts_data
put(path + file_name, "~")
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/network.py", line 677, in host_prompting_wrapper
return func(*args, **kwargs)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/operations.py", line 345, in put
ftp = SFTP(env.host_string)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/sftp.py", line 33, in __init__
self.ftp = connections[host_string].open_sftp()
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/network.py", line 159, in __getitem__
self.connect(key)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/network.py", line 151, in connect
user, host, port, cache=self, seek_gateway=seek_gateway)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/network.py", line 603, in connect
raise NetworkError(msg, e)
NetworkError: Low level socket error connecting to host 54.165.186.168 on port 22: Unable to connect to port 22 on  or 54.165.186.168 (tried 1 time)
[ubuntu@52.90.34.75] put: /home/rerwin21/amazon_proj/amazon/review_page_scraper.py -> /home/ubuntu/review_page_scraper.py
!!! Parallel execution exception under host u'ubuntu@54.173.57.59':
Process ubuntu@54.173.57.59:
Traceback (most recent call last):
 File "/home/rerwin21/anaconda2/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
self.run()
 File "/home/rerwin21/anaconda2/lib/python2.7/multiprocessing/process.py", line 114, in run
self._target(*self._args, **self._kwargs)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/tasks.py", line 242, in inner
submit(task.run(*args, **kwargs))
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/tasks.py", line 174, in run
return self.wrapped(*args, **kwargs)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/decorators.py", line 181, in inner
return func(*args, **kwargs)
 File "<ipython-input-19-ed4344124d24>", line 4, in upload_scripts_data
put(path + file_name, "~")
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/network.py", line 677, in host_prompting_wrapper
return func(*args, **kwargs)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/operations.py", line 345, in put
ftp = SFTP(env.host_string)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/sftp.py", line 33, in __init__
self.ftp = connections[host_string].open_sftp()
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/network.py", line 159, in __getitem__
self.connect(key)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/network.py", line 151, in connect
user, host, port, cache=self, seek_gateway=seek_gateway)
 File "/home/rerwin21/anaconda2/lib/python2.7/site-packages/fabric/network.py", line 603, in connect
raise NetworkError(msg, e)
NetworkError: Timed out trying to connect to 54.173.57.59 (tried 1 time)

答案 1 :(得分：15)

对于EF Core 3.0+，您现在可以使用IsClustered：

modelBuilder.Entity<Person>()
.HasIndex(e => e.UserName)
.IsUnique()
.IsClustered();

.ForSqlServerIsClustered（）现在已标记为过时。

还请注意，如果表上有主键，则可能还需要在将其添加到用户名上之前显式删除其上的群集：

modelBuilder.Entity<Person>()
.HasKey(e => e.PersonId)
.IsClustered(false);

modelBuilder.Entity<Person>()
.HasIndex(e => e.UserName)
.IsUnique()
.IsClustered();

答案 2 :(得分：3)

如果没有内置支持，您可以使用自己的自定义属性来注释模型属性并应用于OnModelCreating()：

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    foreach (var entity in modelBuilder.Model.GetEntityTypes())
    {
        foreach (var prop in entity.GetProperties())
        {
            var attr = prop.PropertyInfo.GetCustomAttribute<IndexAttribute>();
            if (attr != null)
            {
                var index = entity.AddIndex(prop);
                index.IsUnique = attr.IsUnique;
                index.SqlServer().IsClustered = attr.IsClustered;
            }
        }
    }
}

使用简单的标记属性类：

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
public class IndexAttribute : Attribute
{
    public bool IsUnique { get; set; } 
    public bool IsClustered { get; set; } 
}

然后在模型类中，只需添加属性即可创建二级索引：

public class User
{
    public int UserId { get; set; }
    [Index(IsUnique = true, IsClustered = true)]
    public string Nickname { get; set; }
}

答案 3 :(得分：0)

或者这也可行，比如说您想按年龄分组... 

            modelBuilder
            .Entity<Person>()
            .Property(t => t.Age)
            .HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute() { IsClustered = true}));
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