Add new field to every document in a MongoDB collection

Question

How can I add a new field to every document in an existent collection   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 mongo shell

User · Answer

Since MongoDB version 3 2 you can use updateMany     gt  db yourCollection updateMany       set   quot someField quot    quot someValue quot

User · Answer

Same as the updating existing collection field   set will add a new fields if the specified field does not exist   Check out this example    gt  db foo find    gt  db foo insert   test   a     gt  db foo find       id    ObjectId  4e93037bbf6f1dd3a0a9541a     test     a     gt  item   db foo findOne       id    ObjectId  4e93037bbf6f1dd3a0a9541a     test     a     gt  db foo update    id   ObjectId  4e93037bbf6f1dd3a0a9541a       set     new field  1     gt  db foo find       id    ObjectId  4e93037bbf6f1dd3a0a9541a     new field    1   test     a      EDIT   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  db your collection update             set    new field   1       false    true     EDIT   In the above example last 2 fields false  true specifies the upsert and multi flags     Upsert   If set to true  creates a new document when no document matches the query criteria    Multi    If set to true  updates multiple documents that meet the query criteria  If set to false  updates one document   This is for Mongo versions prior to 2 2  For latest versions the query is changed a bit  db your collection update                                 set     new field  1                               upsert false                            multi true

User · Answer

Pymongo 3 9   update   is now deprecated and you should use replace one    update one    or update many   instead   In my case I used update many   and it solved my issue   db your collection update many        set     new field    value     upsert False  array filters None    From documents   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

User · Answer

To clarify  the syntax is as follows for MongoDB version 4 0 x    db collection update      set    new field   1   false true    Here is a working example adding a published field to the articles collection and setting the field s value to true   db articles update      set    published  true   false true

User · Answer

if you are using mongoose try this after mongoose connection async     gt  await Mongoose model  quot collectionName quot   updateMany       set   newField  value

[mongodb] Add new field to every document in a MongoDB collection

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