MongoDB:更新子文档 [英] MongoDB: Updating subdocument

问题描述

我有这个收藏集:

[{ "_id" : 7,
   "category" : "Festival",
   "comments" : [
        {
                "_id" : ObjectId("4da4e7d1590295d4eb81c0c7"),
                "usr" : "Mila",
                "txt" : "This is a comment",
                "date" : "4/12/11"
        }
    ]
}]

我只想在这样的注释中插入一个新字段:

All I want is to push insert a new field inside comments like this:

[{ "_id" : 7,
   "category" : "Festival",
   "comments" : [
        {
                "_id" : ObjectId("4da4e7d1590295d4eb81c0c7"),
                "usr" : "Mila",
                "txt" : "This is a comment",
                "date" : "4/12/11",
                "type": "abc"  // find the parent doc with id=7 & insert this inside comments
        }
    ]
}]

如何在注释子文档中插入

How can I insert inside the comments subdocument?

推荐答案

您需要使用 $位置运算符

例如:

update({ 
       _id: 7, 
       "comments._id": ObjectId("4da4e7d1590295d4eb81c0c7")
   },{
       $set: {"comments.$.type": abc}
   }, false, true
);

我没有测试它，但我希望它对您有帮助.

I didn't test it but i hope that it will be helpful for you.

如果要更改文档的结构，则需要使用

If you want to change the structure of document you need to use

db.collection.update(条件， objNew，upsert，multi)

db.collection.update( criteria, objNew, upsert, multi )

参数:

criteria - query which selects the record to update;
objNew - updated object or $ operators (e.g., $inc) which manipulate the object
upsert - if this should be an "upsert"; that is, if the record does not exist, nsert it
multi - if all documents matching criteria should be updated

并插入具有新结构的新objNew. 查看此详细信息

and insert new objNew with new structure. check this for more details

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