Question

如果在实体框架中使用TPH提供表结构。

class ContactLink {
    Guid Contact_Link_ID { get; set;} //pk
    Guid Tenant_ID { get; set;} //fk
    Guid Contact_ID { get; set;} //fk
}

class ContactLinkCustomer : ContactLink {
    Guid Contact_Link_ID { get; set;} //fk
    Guid Customer_ID { get; set;} //fk
}

如何为拆分合并操作配置弹性比例模式信息，因为实体框架不包含派生类表中的基类属性？特别是Tenant_ID，这是我的点映射分片键。

SchemaInfo schemaInfo = new SchemaInfo();
schemaInfo.Add(new ShardedTableInfo("dbo", "ContactLinkCustomer", ???));
smm.GetSchemaInfoCollection().Add("ShardName", schemaInfo);

更新 ContactLink不是抽象的。

更新2： 我应该注意，ContactLink也在我的DbContext中，并且独立于ContactLinkCustomer进行查询。

更新3： 我没有使用TPH，我们实际上正在使用TPT。这是导致多个表而不是带有鉴别器的单个表的原因。

Answer 1

如果您正在使用TPH并且 ContactLink 和 ContactLinkCustomer 位于同一层次结构中，那么EF应该创建一个包含两个类中所有列的非规范化表。在这种情况下，ContactLink将是分片表，Tenant_ID作为分片键。

但是，如果您真的打算使用多个表，则必须在表中包含 ContactLinkCustomer 的Tenant_ID列，并在Tenant_ID上对其进行分片。当前版本的Elastic Scale库和工具要求分片键出现在参与拆分合并的所有分片表中。

Answer 2

以下对我有用，但需要注意的是，没有数据库级约束可以使Tenant_ID保持同步，因此如果任何代码直接通过T-SQL（而不是通过EF）修改这些表，它们可能会失去同步。

[Table("ContactLink")] // TPT inheritance
class ContactLink
{
    public Guid Contact_Link_ID { get; set; } //pk
    public Guid Tenant_ID { get; set; } //fk
    public Guid Contact_ID { get; set; } //fk
}

[Table("ContactLinkCustomer")] // TPT inheritance
internal class ContactLinkCustomer : ContactLink
{
    // Dummy property to trick EF into creating it as a column for sharding purposes
    // Callers should just directly use the base Tenant_ID property
    // It would be nice if we could set this to be public/protected, but then EF
    // won't create it as a column. Maybe there is a workaround for this?
    [Column("Tenant_ID")]
    public Guid Tenant_ID_ContactLinkCustomer
    {
        get { return base.Tenant_ID; }
        set { base.Tenant_ID = value; }
    }

    public Guid Contact_Link_ID { get; set; } //fk
    public Guid Customer_ID { get; set; } //fk
}

SSMS screenshot

我用于测试的其他课程如下。

class Program
{
    static void Main(string[] args)
    {
        string connStr = "Server=(local);Database=EfShardingTpt;Integrated Security=true";

        using (MyDbContext myDbContext = new MyDbContext(connStr))
        {
            // Drop and recreate database
            Database.SetInitializer(new DropCreateDatabaseAlways<MyDbContext>());
        }

        // Create ContactLinkCustomer
        using (MyDbContext myDbContext = new MyDbContext(connStr))
        {
            ContactLinkCustomer clc = new ContactLinkCustomer
            {
                Contact_ID = Guid.Empty,
                Contact_Link_ID = Guid.Empty,
                Customer_ID = Guid.Empty,
                Tenant_ID = Guid.Parse("00000000-0000-0000-0000-100000000000")
            };

            myDbContext.ContactLinkCustomers.Add(clc);
            myDbContext.SaveChanges();
        }

        WriteTenantIds(connStr);

        // Update through subtype
        using (MyDbContext myDbContext = new MyDbContext(connStr))
        {
            ContactLinkCustomer clc = myDbContext.ContactLinkCustomers.First();
            clc.Tenant_ID = Guid.Parse("00000000-0000-0000-0000-200000000000");
            myDbContext.SaveChanges();
        }

        WriteTenantIds(connStr);

        // Update through supertype
        using (MyDbContext myDbContext = new MyDbContext(connStr))
        {
            ContactLink cl = myDbContext.ContactLinks.First();
            cl.Tenant_ID = Guid.Parse("00000000-0000-0000-0000-300000000000");
            myDbContext.SaveChanges();
        }

        WriteTenantIds(connStr);
    }

    private static void WriteTenantIds(string connectionString)
    {
        using (SqlConnection conn = new SqlConnection(connectionString))
        {
            conn.Open();
            SqlCommand cmd = conn.CreateCommand();

            cmd.CommandText = "SELECT Tenant_ID FROM ContactLink";
            Guid contactLinkTenantId = (Guid) cmd.ExecuteScalar();

            cmd.CommandText = "SELECT Tenant_ID FROM ContactLinkCustomer";
            Guid contactLinkCustomerTenantId = (Guid)cmd.ExecuteScalar();

            Console.WriteLine("{0} {1}", contactLinkTenantId, contactLinkCustomerTenantId);
        }
    }
}

class MyDbContext : DbContext
{
    public MyDbContext(string connectionString) : base(connectionString)
    {
    }

    public virtual DbSet<ContactLink> ContactLinks { get; set; }
    public virtual DbSet<ContactLinkCustomer> ContactLinkCustomers { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<ContactLink>()
            .HasKey(e => e.Contact_Link_ID);

        modelBuilder.Entity<ContactLinkCustomer>()
            .HasKey(e => e.Contact_Link_ID);
    }
}

控制台输出：

00000000-0000-0000-0000-100000000000 00000000-0000-0000-0000-100000000000
00000000-0000-0000-0000-200000000000 00000000-0000-0000-0000-200000000000
00000000-0000-0000-0000-300000000000 00000000-0000-0000-0000-300000000000

也可能存在某种基于映射的解决方案。我尝试了以下但它不起作用。也许通过一些更多的实验它可以工作，但上面的解决方案似乎对我来说足够好所以我没有进一步探索它。

modelBuilder.Entity<ContactLinkCustomer>()
            .Map(m =>
            {
                m.Properties(e => e.Tenant_ID);
                m.ToTable("ContactLinkCustomer");
            });

Unhandled Exception: System.NotSupportedException: The type 'ContactLinkCustomer' cannot be mapped as defined because it maps inherited properties from types th
at use entity splitting or another form of inheritance. Either choose a different inheritance mapping strategy so as to not map inherited properties, or change
all types in the hierarchy to map inherited properties and to not use splitting.

EntityFramework，Azure ElasticScale和Table Per Type（TPT）继承

2 个答案: