文档数据库中的继承? [英] inheritance in document database?

问题描述

我想知道是因为我在 pdf[noSql] 权威指南"和开始 [noSql]"中搜索了继承"这个词，但我什么也没找到?我错过了什么吗?因为我正在使用 hibernate 和 mysql 进行 tablePerHierarchy 继承，所以在 [noSql] 中是否由于某种原因被弃用了?

I am wondering because I searched the pdf "[noSql] the definitive guide" and "beginning [noSql]" for the word "inheritance" but I didn't find anything? am I missing something? because I'm doing a tablePerHierarchy inheritance with hibernate and mysql, does that become deprecated for some reason in [noSql]?

(将[noSql]替换成你喜欢的not only sql"数据库)

(replace [noSql] with the "not only sql" database you like)

推荐答案

我知道这个答案有点晚了，但是对于 MongoDB，您可能会看到一些稍微不同的东西.

I know this answer is a little late, but for MongoDB, you're probably looking at something slightly different.

Mongo 是无模式的，因此tablePerHierarchy"的概念不一定有用.

Mongo is schemaless, so the concept of "tablePerHierarchy" is not necessarily useful.

假设如下

class A
  property X
  property Y
  property Z

class B inherits from A
  property W

在 RDMS 中，你可能会有这样的东西

In an RDMS you would probably have something like this

table A: columns X, Y, Z
table B: columns X, Y, Z, W

但是 MongoDB 没有模式.所以你不需要以这种方式构造数据.相反，您将拥有一个包含所有类型 A 或 B(或 C...)的对象(或文档")的集合".

But MongoDB does not have a schema. So you do not need to structure data in this way. Instead, you would have a "collection" containing all objects (or "documents") of type A or B (or C...).

所以你的收藏将是一系列像这样的对象:

So your collection would be a series of objects like this:

{"_id":"1", "X":1, "Y":2, "Z":3}
{"_id":"2", "X":5, "Y":6, "Z":7, "W":6}

您会注意到，我将 A 类型的对象存储在 B 类型的对象旁边.MongoDB 使这变得非常容易.只需从集合中拉出一个文档，它就会神奇地"拥有所有适当的字段/属性.

You'll notice that I'm storing objects of type A right beside objects of type B. MongoDB makes this very easy. Just pull up a Document from the Collection and it "magically" has all of the appropriate fields/properties.

但是，如果您有数据对象"或实体"，则可以通过添加类型使您的生活更轻松.

However, if you have "data objects" or "entities", you can make your life easier by adding a type.

{"_id":"1", "type":"A", "X":1, "Y":2, "Z":3}
{"_id":"2", "type":"B", "X":5, "Y":6, "Z":7, "W":6}

这样可以更轻松地编写用于加载对象的工厂类.

This makes it easier to write a factory class for loading your objects.

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