使用 GORM 无需再次访问数据库即可获取一对多加载对象的 ID [英] Getting the ID of a one-to-many loaded object without another trip to the DB with GORM

问题描述

我必须 GORM 域，A &B、与数据库表有关.A 与 B 是一对多的关系.因此，这些类看起来类似于:

I have to GORM domains, A & B, that relate to database tables. A has a one-to-many relationship with B. Because of this, the classes look similar to:

class A {
   B b
   Long id
}

class B {
   Long id
}

当我检索 A 的实例时，会从数据库中检索 B 的相应实例的 ID.但是，当我尝试通过以下方式访问该 ID 时:

When I retrieve an instance of A the ID of the corresponding instance of B is retrieved from the database. However, when I attempt to access that ID via something like:

A a = A.get(11)
Long bid = a.b.id

整个对象从数据库加载.在某些情况下，我只想要 B 的 ID(已经被检索到)并且不想从数据库加载整个实例.有没有办法从 B 获取 ID，而无需返回并获取整个对象.

the whole object is loaded from the database. In some cases I only want the ID of B (which has already been retrieved) and do not want to load the whole instance from the database. Is there a way to get the ID from B without going back and fetching the whole object.

注意:我知道它在上面的 abid 行上做了一个额外的提取，因为我可以看到自从我打开 loggingSql 选项后生成的 SQL在我的数据源文件中.

NOTE: I know that it is doing an extra fetch on the line with a.b.id above because I can see the SQL being generated since I turned on the loggingSql option in my DataSource file.

推荐答案

代替:

多头出价 = a.b.id

Long bid = a.b.id

使用:

多头出价 = a.bId

Long bid = a.bId

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