使用Mongodb将元素推送到数组内的数组

Question

大家好，我是mongodb的新手，坦率地说，这对我来说仍然是一个令人困惑的报价，因为我已经习惯了mysql，而且对json的了解也较少。

这是我从集合讨论中获得的文档

{
        "_id" : ObjectId("5188c93f0361ca6dc33e3a30"),
        "admin" : [ ],
        "created" : "2013-04-30 19:10:21",
        "description" : "guitar theory",
        "members" : [ ],
        "modified" : "2013-04-30 19:10:21",
        "name" : "Arpeggios",
        "posts" : [
                {
                        "post_id" : "1",
                        "user_id" : "1",
                        "name" : "Test",
                        "slug" : "xxx",
                        "comment" : "xxx",
                        "created" : "xxx",
                        "modified" : "xxx",
                        "comments" : [ ],
                        "attachments" : [ ]
                },
                {
                        "post_id" : "2",
                        "user_id" : "1",
                        "name" : "Test",
                        "slug" : "xxx",
                        "comment" : "xxx",
                        "created" : "xxx",
                        "modified" : "xxx",
                        "comments" : [ ],
                        "attachments" : [ ]
                }
        ],
        "profile_pic" : "adasdad",
        "settings" : [ ],
        "slug" : "arpeggio"
}

我的目标是在数组注释上推入一个post_id = 1的元素，以得到我想要的结果：

{
        "_id" : ObjectId("5188c93f0361ca6dc33e3a30"),
        "admin" : [ ],
        "created" : "2013-04-30 19:10:21",
        "description" : "guitar theory",
        "members" : [ ],
        "modified" : "2013-04-30 19:10:21",
        "name" : "Arpeggios",
        "posts" : [
                {
                        "post_id" : "1",
                        "user_id" : "1",
                        "name" : "Test",
                        "slug" : "xxx",
                        "comment" : "xxx",
                        "created" : "xxx",
                        "modified" : "xxx",
                        "comments" : [ 
                        {"comment_id":"xxx", "user_id":"xxx", "name":"xxx","comment":"xxx", "created":"xxx", "modified":"xxx"},
                        {"comment_id":"xxx", "user_id":"xxx", "name":"xxx","comment":"xxx", "created":"xxx", "modified":"xxx"}
                        ],
                        "attachments" : [ ]
                },
                {
                        "post_id" : "2",
                        "user_id" : "1",
                        "name" : "Test",
                        "slug" : "xxx",
                        "comment" : "xxx",
                        "created" : "xxx",
                        "modified" : "xxx",
                        "comments" : [ ],
                        "attachments" : [ ]
                }
        ],
        "profile_pic" : "adasdad",
        "settings" : [ ],
        "slug" : "arpeggio"
} 

我已经彻底研究了几个小时，这是我想出来的，这只是一个失败，不起作用：

db.discussions.update(
                {_id:ObjectId("5188c93f0361ca6dc33e3a30"), posts:{post_id:1}}, 
                {$push:
                    {"posts:
                        {comments:
                            {"comment_id":"xxx", "user_id":"xxx", "name":"xxx","comment":"xxx", "created":"xxx", "modified":"xxx"}
                        }
                    } 
                }
                )

伙计们，我在拼命地寻求帮助。我想学习这方面的知识。

Answer 1

有几件事正在发生。

首先，您想使用the $ positional operator。

其次，您提到您的集合名称是讨论，但您的更新使用了“讨论”-确保您使用与实际集合名称相同的名称。

第三，您在列出的文档中的post_id是" 1“，但您正在尝试匹配1。字符串"1”将不等于数字1。请注意您的类型。

这个语法(请注意，我还更正了不平衡的引号)应该可以做到：

db.discussion.update(
             {_id:ObjectId("5188c93f0361ca6dc33e3a30"), "posts.post_id":"1"},
             {$push:
                  {"posts.$.comments":
                         {"comment_id":"xxx", "user_id":"xxx",
                          "name":"xxx","comment":"xxx", "created":"xxx",
                           "modified":"xxx"}
                     }
                 }
              )

我要重申我不喜欢这种模式--你没有限制你的文档增长，这会导致性能问题，更不用说让它变得比你需要的更复杂(也更大)。