使用 MongoMapper 根据数组的大小对 MongoDB 中的项目进行排序？

发布于 2024-08-19 08:06:44 字数 331 浏览 7 评论 0原文

我想选择根据数组中的项目数量排序的项目集合。希望下面的示例能够澄清我相当糟糕的解释：

class Thing
  include MongoMapper::Document

  key :name, String
  key :tags, Array
end

我想检索从标签最多到标签最少的所有 Thing。此示例中的标签只是标签数组中的字符串。基本上我想要的东西与此含义相同（但有效）：

Thing.all(:order => 'tags.count desc')

这可能吗？

原文

I'd like to select a collection of items ordered based on the number of items within an array. Hopefully the following example will clarify my rather poor explanation:

class Thing
  include MongoMapper::Document

  key :name, String
  key :tags, Array
end

I'd like to retrieve all Things ordered from those with the most tags to those with the least. The tags in this example are simply strings within the tags array. Basically I want something which means the same as this (but works):

Thing.all(:order => 'tags.count desc')

Is this possible?

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

风和你 2024-08-26 08:06:44

核心服务器当前不支持计算数组的大小，然后按该大小进行排序。我认为目前最好的选择是自己缓存数组大小，并在该字段上添加索引。

class Thing
  include MongoMapper::Document

  key :name,     String
  key :tags,     Array
  key :tag_size, Integer, :default => 0, :index => true
end

然后只需向您的模型添加一个回调，以在保存时更新 tag_size 。

如果这是您希望在核心服务器中看到的功能，您可以在此处添加一个案例：

http ://jira.mongodb.org/browse/SERVER

The core server currently doesn't support computing the size of an array and then sorting by that. I think that your best bet for the moment would be to cache the array size on your own, and add an index on that field.

class Thing
  include MongoMapper::Document

  key :name,     String
  key :tags,     Array
  key :tag_size, Integer, :default => 0, :index => true
end

Then just add a callback to your model that updates tag_size on save.

If this is a feature you'd like to see in the core server, you can add a case here:

http://jira.mongodb.org/browse/SERVER

回复收藏 0 原文

~没有更多了~