在简单的Add（）-> SaveChanges（）上被选为死锁受害者

Question

这个简单的程序

private static void Main(string[] args)
{
    Parallel.For(0, 1000000, InsertTestEntity);
}

private static void InsertTestEntity(int i)
{
    using (var dbContext = new TestDbContext())
    {
        dbContext.TestEntities.Add(new TestEntity { HugeString = "Baby shark," + string.Join(", ", Enumerable.Repeat("doo", 500)) });
        dbContext.SaveChanges();
    }
}

public class TestEntity
{
    [Key]
    public int Id { get; set; }

    public string HugeString { get; set; }
}

public class TestDbContext : DbContext
{
    public DbSet<TestEntity> TestEntities { get; set; }
}

引发类似

的异常

System.Data.Entity.Infrastructure.DbUpdateException
  HResult=0x80131501
  Message=An error occurred while updating the entries. See the inner exception for details.
  Source=EntityFramework
  StackTrace:
   at System.Data.Entity.Internal.InternalContext.SaveChanges()
   at System.Data.Entity.Internal.LazyInternalContext.SaveChanges()
   at System.Data.Entity.DbContext.SaveChanges()
   at EntityFrameworkStressTest.Program.InsertTestEntity(Int32 i) in c:\Git\EntityFrameworkStressTest\EntityFrameworkStressTest\Program.cs:line 18
   at System.Threading.Tasks.Parallel.<>c__DisplayClass17_0`1.<ForWorker>b__1()

Inner Exception 1:
UpdateException: An error occurred while updating the entries. See the inner exception for details.

Inner Exception 2:
SqlException: Transaction (Process ID 100) was deadlocked on lock | communication buffer resources with another process and has been chosen as the deadlock victim. Rerun the transaction.

SQL表在SSMS中看起来像这样

Answer 1

从SSMS屏幕截图中可以看出，似乎没有主键的迹象。 ID列旁边应该有一个钥匙符号。

进一步检查发现，Id的确声明为身份（用于AUTO INCREMENT的SQL Server），但未声明为主键。要使Id成为真正的主键，请右键单击SSMS中的表，然后选择“设计”，右键单击列设计器中的Id行，然后单击“设置主键”：

此后，压力测试将运行而不会死锁。