查询Mongo中的嵌套列表存在 [英] Querying Nested List Existence in Mongo

问题描述

我在Mongo中有一个文档，其结构如下：

I have a document in Mongo that is structured in the following way:

{ 
    "_id" : ObjectId("4eea7237d0ba3a04f20008fb"), 
    "code" : "b2677c2809c844cc9d7e3e4ff8d95b46", 
    "city_id" : 4, 
    "datetime" : ISODate("2011-12-13T18:41:44.062Z"), 
    "plays" : [     
        {   
          "play_id" : 717224,   
          "clicks" : [ ],   
          "order" : 1,  
          "mysql_id" : 145
        }

我想查询其播放的文档。 clicks属性是一个非空列表。我试过没有运气的存在。我认为这样的事情可能有用：

I want to query for docs whose plays.clicks attribute is a non-empty list. I've tried exists with no luck. I thought that something like this might work:

 db.collection.find({plays.clicks.0: {$exists:true}})

但我相信这只会返回播放数组中第一个元素包含的文档非空的点击列表。

But I believe that this would return only docs whose first element in the plays array contains a non-empty clicks list.

我是否想过如何完成这项工作？

Any thought on how I might get this done?

谢谢

推荐答案


db.collection.find（{plays.clicks.0：{$ exists：true}}）


是正确的语法，但是当播放是一个列表，查询将匹配任何 c>点击的文件 。没有办法以这种方式为子元素检索数组的子集[1]。有一个子/虚拟馆藏票[2]

is the right syntax, however as plays is a list the query will match any document that has clicks in plays. There is no way to retrieve a subset of an Array for subelements in this way[1]. There is a ticket for sub / virtual collections[2]

[1] http://www.mongodb.org/display/DOCS/Retrieving+a+Subset+of+Fields#RetrievingaSubsetofFields-RetrievingaSubrangeofArrayElements

[2] https：// jira .mongodb.org / browse / SERVER-828

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