NHibernate - 映射到辅助键的最佳方式

发布于 2024-09-13 09:38:35 字数 996 浏览 2 评论 0原文

我正在尝试将新的域模型映射到固定模式遗留数据库，但一直困惑于如何进行某种类型的映射。这是我的问题的摘要。

工人有多种类型。例如，HourlyWorker 和 SalariedWorker。

HourlyWorker 的数据存储在 WORKERS 表和 HOURLY_WORKERS 表中，两者之间具有标准外键关系 WORKERS.PK_WORKERS = HOURLY_WORKERS.FK_WORKERS。

从 NHibernate 的角度来看，HourlyWorker 的“Id”被映射到 WORKERS.PK_WORKERS，这是应该的。

到目前为止，一切都很好。

现在假设有一个对象仅适用于小时工。

class Timesheet
  HourlyWorker Owner { get; private set; }

在旧数据库中，它以一种相当简单的方式映射到 TIMESHEETS 表，但有一个问题：到所有者的外键链接不是通过到 WORKER 表的链接来表达的，而是通过到 HOURLY_WORKER 表的链接来表达的。换句话说，外键 FK_HOURLY_WORKER 是一个唯一标识符，但不指向 NHibernate 视图中主键的值。

我不能简单地将 Id HourlyWorker 更改为映射到 HOURLY_WORKER 表，因为 70% 引用小时工的数据库使用 WORKER 中的主键作为外键 Id。

映射此关系的选项有哪些？

可能会使此过程变得更容易：所有者属性是只读的 - 时间表无法更改其所有者。但是，当删除 HourlyWorker 时，删除应级联到其所有时间表。

最后，请不要回复建议我更改数据库。我知道。如果您想要我客户的电话号码，以便您可以尝试说服他们，他们的架构并不是现有的最完美的东西，那么我可以提供。我已经为这场斗争奋斗了几个月。另外，请不要回应说这表明问题是管理问题而不仅仅是 NHibernate 映射问题。我也知道这一点。目前，我只想获得有关如何解决技术问题的建议。

原文

I am trying to map a new domain model to a fixed-schema legacy database and am stuck on how to do a certain type of mapping. Here's a distilation of my problem.

There are types of Workers. For example an HourlyWorker and a SalariedWorker.

The data for an HourlyWorker is stored in the WORKERS table and the HOURLY_WORKERS table with a standard foreign key relation between the two of WORKERS.PK_WORKERS = HOURLY_WORKERS.FK_WORKERS.

The "Id" of the HourlyWorker from NHibernate's point of view is mapped to WORKERS.PK_WORKERS, which is as it should be.

So far so good.

Now suppose there is an object that applies only to hourly workers.

class Timesheet
  HourlyWorker Owner { get; private set; }

In the legacy database this maps to the TIMESHEETS table in a fairly straightforward manner but with one catch: The foreign-key link to the owner is expressed not through a link to the WORKER table but via a link to the HOURLY_WORKER table. In other words, the foreign key FK_HOURLY_WORKER is a unique identifier but is not pointing at the value that is in NHibernate's view the primary key.

I cannot simply change the Id HourlyWorker to map to the HOURLY_WORKER table because 70% of the database referencing houry workers uses the primary key from WORKER as the foreign key Id.

What are my options for mapping this relationship?

Something that might make this easier: the Owner property is read only - the Timesheet cannot have it's owner changed. However, when an HourlyWorker is deleted, deletes should cascade to all of their Timesheets.

Finally, please don't respond with recommendations that I change the database. I know. If you want my client's phone number so that you can try to convince them that their schema is not the most perfect thing in existence then I can supply it. I have been fighting this fight for months. Also please don't respond that this indicates that the problem is managerial and not just NHibernate mappings. I know that too. For right now, I just want advice on how to solve the technical problem.

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