向 MongoDB 集合中的每个文档添加新字段
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Add new field to every document in a MongoDB collection
提问by itsme
How can I add a new field to every document in an existent collection?
如何向现有集合中的每个文档添加新字段？
I know how to update an existing document's field but not how to add a new field to every document in a collection. How can I do this in the mongoshell?
我知道如何更新现有文档的字段，但不知道如何向集合中的每个文档添加新字段。我怎样才能在mongoshell 中做到这一点？
回答by RameshVel
Same as the updating existing collection field, $setwill add a new fields if the specified field does not exist.
与更新现有集合字段相同，$set如果指定字段不存在，将添加新字段。
Check out this example:
看看这个例子：
> db.foo.find()
> db.foo.insert({"test":"a"})
> db.foo.find()
{ "_id" : ObjectId("4e93037bbf6f1dd3a0a9541a"), "test" : "a" }
> item = db.foo.findOne()
{ "_id" : ObjectId("4e93037bbf6f1dd3a0a9541a"), "test" : "a" }
> db.foo.update({"_id" :ObjectId("4e93037bbf6f1dd3a0a9541a") },{$set : {"new_field":1}})
> db.foo.find()
{ "_id" : ObjectId("4e93037bbf6f1dd3a0a9541a"), "new_field" : 1, "test" : "a" }
EDIT:
编辑：
In case you want to add a new_field to all your collection, you have to use empty selector, and set multi flag to true (last param) to update all the documents
如果要向所有集合添加 new_field，则必须使用空选择器，并将 multi 标志设置为 true（最后一个参数）以更新所有文档
db.your_collection.update(
{},
{ $set: {"new_field": 1} },
false,
true
)
EDIT:
编辑：
In the above example last 2 fields false, truespecifies the upsertand multiflags.
在上面的例子中，最后 2 个字段false, true指定了upsert和multi标志。
Upsert:If set to true, creates a new document when no document matches the query criteria.
Upsert：如果设置为 true，则在没有文档与查询条件匹配时创建一个新文档。
Multi:If set to true, updates multiple documents that meet the query criteria. If set to false, updates one document.
Multi：如果设置为 true，则更新满足查询条件的多个文档。如果设置为 false，则更新一个文档。
This is for Mongo versionsprior to 2.2. For latest versions the query is changed a bit
这是针对 Mongoversions之前的2.2。对于最新版本，查询略有变化
db.your_collection.update({},
{$set : {"new_field":1}},
{upsert:false,
multi:true})
回答by LineDrop
To clarify, the syntax is as follows for MongoDB version 4.0.x:
澄清一下，MongoDB 4.0.x 版的语法如下：
db.collection.update({},{$set: {"new_field*":1}},false,true)
Here is a working example adding a publishedfield to the articlescollection and setting the field's value to true:
这是一个向文章集合添加已发布字段并将该字段的值设置为true的工作示例：
db.articles.update({},{$set: {"published":true}},false,true)
回答by Alex Jolig
Pymongo 3.9+
派蒙戈 3.9+
update()is now deprecatedand you should use replace_one(), update_one(), or update_many()instead.
update()现在已弃用，您应该使用replace_one(), update_one(), 或update_many()代替。
In my case I used update_many()and it solved my issue:
在我的情况下，我使用update_many()并解决了我的问题：
db.your_collection.update_many({}, {"$set": {"new_field": "value"}}, upsert=False, array_filters=None)
From documents
从文件
update_many(filter, update, upsert=False, array_filters=None, bypass_document_validation=False, collation=None, session=None) filter: A query that matches the documents to update. update: The modifications to apply. upsert (optional): If True, perform an insert if no documents match the filter. bypass_document_validation (optional): If True, allows the write to opt-out of document level validation. Default is False. collation (optional): An instance of Collation. This option is only supported on MongoDB 3.4 and above. array_filters (optional): A list of filters specifying which array elements an update should apply. Requires MongoDB 3.6+. session (optional): a ClientSession.
update_many(filter, update, upsert=False, array_filters=None, bypass_document_validation=False, collation=None, session=None) filter: A query that matches the documents to update. update: The modifications to apply. upsert (optional): If True, perform an insert if no documents match the filter. bypass_document_validation (optional): If True, allows the write to opt-out of document level validation. Default is False. collation (optional): An instance of Collation. This option is only supported on MongoDB 3.4 and above. array_filters (optional): A list of filters specifying which array elements an update should apply. Requires MongoDB 3.6+. session (optional): a ClientSession.
