猫鼬查询嵌套文档或多或少的某个日期

问题描述：

我如何查询大于或小于特定日期的评论...

How dow I query comments greater than or less than a certain date...

这是我的带有Post模型和Comment模型的架构:

Here is my Schema with Post model and a Comment model:

var mongoose = require('mongoose');
var should = require('should');

mongoose.connect("localhost","test_db");

var CommentSchema = new mongoose.Schema({
  content:    {type:String},
  created_at: {type:Date, default:Date.now}

});

var PostSchema = new mongoose.Schema({
  title:    {type:String},
  content:  {type:String},
  comments: [CommentSchema]

    });

var Post = mongoose.model('Post',PostSchema);
var Comment = mongoose.model('Comment',CommentSchema);

var post = new Post({title:"hello world",comments:[{content:"1st comment"},{content:"2nd comment"}]});
// I saved it! and then I query for it

  var id = "5045d5be48af9f040f000002";
  Post.find({ _id:id,
              "comments.created_at":{ $gte:(new Date())}
                },function(err,result){
    console.log(result);
  });

我需要有关嵌入式文档查询的帮助...

I need help with querying the embedded docs...

好吧，我编辑了代码以提供更多细节.

Ok I edited my code to give more detail.

这将返回一个空数组.所以我想要或期望的是一个带有空评论数组的帖子.但是用这个查询我什么都没有得到. (当我将$ gte与$ lte交换时，(显然)该帖子带有2条评论).

This returns an empty array. So what I want or what I would expect is a Post with an empty comments array. But with this query I do not get a post at all. (when I exchange $gte with $lte I get (obviously) the post with its 2 comments).

但是我又该如何根据我上面的描述过滤详细信息?

But again how can I filter the details so according to my description above?

答

使用点符号以进入嵌入式数组文档的内部.例如，要查询Post在date1和date2之间的created_at注释:

Use dot notation to reach inside the embedded array docs. For example, to query for the Post comments with a created_at between date1 and date2:

Post.find({ "comments.created_at": { $gt: date1, $lt: date2 }}, function (err, docs) {
     ...
});

更新

感谢您的修改；现在，我了解到您正在尝试按created_at日期过滤单个帖子的评论.您不能直接使用MongoDB查询来做到这一点，但是我相信如果您使用的是2.2版本的聚合框架，则可以做到这一点.看看有关Jira上功能请求的讨论.

Thanks for the edit; now I understand that you're trying to to filter the comments of single post by their created_at date. You can't do that directly with MongoDB queries, but I believe you can do it with the 2.2 aggregation framework if you're at that version. Take a look at the discussion of this feature request on Jira for examples.

猫鼬查询嵌套文档或多或少的某个日期

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