Python 无需重新插入即可将项目附加到 PyMongo 中的 MongoDB 文档数组

Append item to MongoDB document array in PyMongo without re-insertion

提问by deadbits

I am using MongoDB as the back-end database for Python web application (PyMongo + Bottle). Users can upload files and optionally 'tag' these files during upload. The tags are stored as a list within the document, per below:

我使用 MongoDB 作为 Python Web 应用程序 (PyMongo + Bottle) 的后端数据库。用户可以上传文件，并可以在上传过程中选择“标记”这些文件。标签作为列表存储在文档中，如下所示：

{
    "_id" : ObjectId("561c199e038e42b10956e3fc"),
    "tags" : [ "tag1", "tag2", "tag3" ],
    "ref" : "4780"
}

I am trying to allow users to append new tags to any document. I came up with something like this:

我试图允许用户将新标签附加到任何文档。我想出了这样的事情：

def update_tags(ref, new_tag)
    # fetch desired document by ref key as dict
    document = dict(coll.find_one({'ref': ref}))
    # append new tag
    document['tags'].append(new_tag)
    # re-insert the document back into mongo
    coll.update(document)

(fyi; refkey is always unique. this could easily be _idas well.) It seems like there should be a way to just update the 'tags' value directly without pulling back the entire document and re-inserting. Am I missing something here?

（仅供参考；ref键总是唯一的。这也很容易_id。）似乎应该有一种方法可以直接更新“标签”值，而无需拉回整个文档并重新插入。我在这里错过了什么吗？

Any thoughts are greatly appreciated :)

任何想法都非常感谢:)

采纳答案by styvane

You don't need to use to retrieve the document first just use the .updatemethod with the $pushoperator.

您不需要先使用来检索文档，只需使用.update带有$push操作符的方法即可。

def update_tags(ref, new_tag):
    coll.update({'ref': ref}, {'$push': {'tags': new_tag}})

Since update is deprecated you should use the find_one_and_updateor the update_onemethod if you are using pymongo 2.9 or newer

由于更新已弃用，如果您使用的是 pymongo 2.9 或更高版本，则应使用find_one_and_update或update_one方法

回答by Kiluvya.A

Just to add to @ssytvane answer,and to answer @Guarav: you can add "upsert = True" if it does not exist:

只是为了添加到@ssytvane 答案，并回答@Guarav：如果它不存在，您可以添加“upsert = True”：

def update_tags(ref, new_tag):
    coll.update({'ref': ref}, {'$push': {'tags': new_tag}}, upsert = True)

or

或者

def update_tags(ref, new_tag):
    coll.update_one({'ref': ref}, {'$push': {'tags': new_tag}}, upsert = True)

回答by Nikhil Fulzele

You can simply do

你可以简单地做

1) If you want to append single entry

1）如果你想附加单个条目

def update_tags(ref, new_tag):
    coll.update({'ref': ref}, {'$push': {'tags': new_tag}})

eg:

例如：

{
    "_id" : ObjectId("561c199e038e42b10956e3fc"),
    "tags" : [ "tag1", "tag2", "tag3" ],
    "ref" : "4780"
}
>> update_tags("4780", "tag4")
{'updatedExisting': True, u'nModified': 1, u'ok': 1, u'n': 1}
>> coll.find_one({"ref":"4780"})
{
    "_id" : ObjectId("561c199e038e42b10956e3fc"),
    "tags" : [ "tag1", "tag2", "tag3" , "tag4" ],
    "ref" : "4780"
}

2) If you want to append multiple entries

2) 如果要附加多个条目

def update_tags(ref, new_tag):
    coll.update({'ref': ref}, {'$pushAll': {'tags': new_tag}}) #type of new_tag is list

eg:

例如：

{
    "_id" : ObjectId("561c199e038e42b10956e3fc"),
    "tags" : [ "tag1", "tag2", "tag3" ],
    "ref" : "4780"
}
>> update_tags("4780", ["tag5", "tag6", "tag7"])
{'updatedExisting': True, u'nModified': 1, u'ok': 1, u'n': 1}
>> coll.find_one({"ref":"4780"})
{
    "_id" : ObjectId("561c199e038e42b10956e3fc"),
    "tags" : [ "tag1", "tag2", "tag3" , "tag4" , "tag5", "tag6", "tag7" ],
    "ref" : "4780"
}

Note: If the key is not already present, then mongo will create new key.

注意：如果密钥不存在，则 mongo 将创建新密钥。

回答by ArminMz

There had been some good answers that are correct but in my opinion writing update_tags this way is better and more usable:

有一些很好的答案是正确的，但在我看来，以这种方式编写 update_tags 更好，更有用：

def update_tags(ref, *args):
    coll.update_one(ref, {'$push': {'tags': {'$each': args}}})

this way you can do both appending one tag or appending many tags:

通过这种方式，您既可以附加一个标签，也可以附加多个标签：

>> update_tags(ref, 'tag5')

>> update_tags(ref, 'tag5', 'tag6')

>> list_of_new_tags = do_something_that_returns_list_of_tags()
>> update_tags(ref, *list_of_new_tags)