与猫鼬一对多

问题描述

我想定义学生模型和编队模型之间的一对多关系:1个学生属于1个编队，一个编队可以由N个学生组成.

I want to define a one-to-many relationship between my Student model and my Formation model: 1 student belongs to 1 formation and a formation can be composed of N students.

我的需求是:

• 能够使用其学生填充编队"文档
• 轻松检索学生的构成

所以我写道:

let student = new Schema({
    firstName: {
        type: String
    },
    lastName: {
        type: String
    },
    formation : {
        type: Schema.Types.ObjectId,
        ref: 'Formation'
    }
});

let formation = new Schema({
    title: {
        type: String
    },
    students: [{ type: Schema.Types.ObjectId, ref: 'Student' }]
}

当我搜索有关与mongodb/mongoose一对多关系的文档时，我很惊讶地看到，当我想创建一个Student文档(并将其添加到队形中)时，我一定不会仅将其"formation"字段设置为formation id，并将其推送到formation文档的"students"字段.
是否意味着当我想用另一个班级替换学生的班级时，我将需要1/更新其班级字段2/将自己的学生ID从班级学生"字段中删除，然后将其重新添加到学生领域的新形成?
对我来说似乎有点多余.我想念什么吗?

When I'm searching for documentation about the one-to-many relation with mongodb/mongoose, I'm surprised to see that when I want to create a Student document (and add it to a formation), I must not only set its "formation" field with the formation id and also push it to the formation document "students" field.
Does it imply that when I want to replace the formation of a student with another formation, I'll need to 1/ update its formation field 2/ remove myself the student id from the formation "students" field and re-add it to the students field of the new formation?
It seems a little redundant to me. Am I missing something?

推荐答案

在队形模型上使用students既不好，也是多余的.潜在的无限数组设计不佳，因为它们可能导致达到文档大小限制.关于冗余，在这种情况下，您只有两个查询:

Having students on the Formation model is both bad practice and redundant. Potentially infinite arrays are a poor design as they can lead to hitting document size limits. In regards to being redundant, you only have two queries in this situation:

1)您的内存中有一个student，并且您想查找其形成:

1) You have a student in memory, and you want to find their formation:

Formation.findOne({_id: student.formation},callback);

2)您的记忆中有一个formation，并希望找到该编队的所有学生:

2) You have a formation in memory, and want to find all students in that formation:

Student.find({formation: formation._id}, callback);

两者都不需要在队形架构上具有students.

Neither of which require having students on the Formation schema.

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