GAE组织数据结构问题 [英] GAE organizing data structure problem

问题描述

好的。我正在与GAE合作。我想创建这样的东西：

我有类型grouptopictag：

>

每个群组可以根据需要拥有多少
个主题 每个主题可以根据需要添加尽可能多的标签

group可以根据需要具有尽可能多的标签

。

现在我有这样的：

  class TopicGroup （db.Model）：
 title = db.StringProperty（required = True）
 
 class Topic（db.Model）：
 title = db.StringProperty 
 group = db.ReferenceProperty（TopicGroup，'group'，'topics'，required = True）
 
 class TopicTag（db.Model）：
 topic = db.ReferenceProperty 
 group = db.ReferenceProperty（TopicGroup，'group'，'tags'，required = True）
 value = db.StringProperty（required = True）
  

但这不好（在我的模型主题只能有一个标签，我已经有一个裂缝在我的头...是否有人可以帮助？

>

解决方案

多对多连接可以实现为连接表（或关系模型）。在下面的解决方案中，有一个模型包含应用于个人组（ GroupTags ）的所有标签和一个保存应用于 Topics （ TopicTags ）的标签的模型。

从标签的引用中解除标签本身允许您执行更改拼写标签，而不需要更新每个标签 c 或主题 code>。

此外，该模型充分利用了AppEngine对具有引用它们的其他实体的实体创建自动反向引用的事实。在下面的模型中，一个Group实体将有一个名为 topics 的属性，它将获取所有 Topic 实体组的引用指向组。类似地，每个 Group 从 GroupsTags 获取标签模型，它给它属于它的所有标签实体。每个标签实体获得一个组和主题属性

这是一个非常强大的函数，它是一个非常强大的函数，

  class Group（db.Model）：
＃我的所有群组特定数据。 
 
 class Topic（db.Model）：
 title = db.StringProperty（required = True）
 group = db.ReferenceProperty（Group，collection ='topics'）
＃其他主题特定数据。 
 
 class Tag（db.Model）：
 text = db.StringProperty（required = True）
 
 class GroupTags（db.Model）：
 group = db.ReferenceProperty（Group，collection ='tags'）
 tag = db.ReferenceProperty（Tag，collection ='groups'）
 
 class TopicTags（db.Model）：
 topic = db.ReferenceProperty（Topic，collection ='tags'）
 tag = db.ReferenceProperty（Tag，collection ='topics'）
  

Ok. I'm working with GAE. And i want create something like this:

I have types "group" "topic" "tag":

1. each "group" can have as many "topics" as needed

2. each "topic" can have as many "tags" as needed

3. each "group" can have as many "tags" as needed

it's something like circle.

right now i have something like this:

class TopicGroup(db.Model):
    value = db.StringProperty(required=True)

class Topic(db.Model):
    title = db.StringProperty(required=True)
    group = db.ReferenceProperty(TopicGroup, 'group', 'topics', required=True)

class TopicTag(db.Model):
    topic = db.ReferenceProperty(Topic, 'topic', 'tags', required=True)
    group = db.ReferenceProperty(TopicGroup, 'group', 'tags', required=True)
    value = db.StringProperty(required=True)

but this is no good (in my model "topic" can have only one tag, but i nead "topic" to have as many tags as needed)

well i already have a crack in my head... is there someone who could help?

解决方案

Many-to-many joins can be implemented as join tables (or Relationship Models). In the solution below, there is a model that holds all of the tags that are applied to individual Groups (GroupTags) and a model that holds the tags that are applied to Topics (TopicTags).

Decoupling the Tag itself from references to the Tag allows you to do things like change the spelling of a tag without needing to update every Group or Topic to which that Tag is applied.

Also, this model takes good advantage of the fact that AppEngine creates automatic backreferences on entities that have other entities referencing them. In the models below, a Group entity will have a property called topics that is a query that will fetch all Topic entities who's group reference points to that Group. Similarly, each Group gets a tags property from the GroupsTags model that gives it all of the Tag entities that belong to it. Every Tag entity gets a groups and topics property that is a query for all of the entities of those types that have the give Tag assigned, making searching by tag (a very typical operation) quite simple.

It's a very powerful and flexible approach to modeling systems such as yours.

class Group(db.Model):
    # All of my group-specific data here.

class Topic(db.Model):
    title = db.StringProperty(required=True)
    group = db.ReferenceProperty(Group, collection='topics')
    # other topic-specific data here.

class Tag(db.Model):
    text = db.StringProperty(required=True)

class GroupTags(db.Model):
    group = db.ReferenceProperty(Group, collection='tags')
    tag = db.ReferenceProperty(Tag, collection='groups')

class TopicTags(db.Model):
    topic = db.ReferenceProperty(Topic, collection='tags')
    tag = db.ReferenceProperty(Tag, collection='topics')

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