Update Methods
MongoDB provides the following methods for updating documents in a collection:
| Method | Description |
| db.collection.updateOne() |
Updates at most a single document that match a specified filter even though multiple documents may match the specified filter. New in version 3.2. |
| db.collection.updateMany() |
Update all documents that match a specified filter. New in version 3.2. |
| db.collection.replaceOne() |
Replaces at most a single document that match a specified filter even though multiple documents may match the specified filter. New in version 3.2. |
| db.collection.update() |
Either updates or replaces a single document that match a specified filter or updates all documents that match a specified filter. By default, the db.collection.update() method updates a single document. To update multiple documents, use the multi option. |
These methods accept as parameters:
- a filter document to determine which documents to update. These filters use the same syntax as read operations:
- A query filter document can specify equality condition with <field>:<value> expressions to select all documents that contain the <field> with the specified <value>:
{ <field1>: <value1>, ... } - A query filter document can use the query operators to specify conditions in the following form:
{ <field1>: { <operator1>: <value1> }, ... }
- A query filter document can specify equality condition with <field>:<value> expressions to select all documents that contain the <field> with the specified <value>:
- an update document to specify the modification to perform or a replacement document that wholly replaces the matching documents except for the _id field, and
- an options document.
Behavior
Atomicity
All write operations in MongoDB are atomic on the level of a single document. For more information on MongoDB and atomicity, see Atomicity and Transactions.
_id Field
Once set, you cannot update the value of the _id field nor can you replace an existing document with a replacement document that has a different _id field value.
Document Size
When performing update operations that increase the document size beyond the allocated space for that document, the update operation relocates the document on disk.
Field Order
MongoDB preserves the order of the document fields following write operations except for the following cases:
- The _id field is always the first field in the document.
- Updates that include renaming of field names may result in the reordering of fields in the document.
Changed in version 2.6: Starting in version 2.6, MongoDB actively attempts to preserve the field order in a document. Before version 2.6, MongoDB did not actively preserve the order of the fields in a document.
Upsert Option
If db.collection.update(), db.collection.updateOne(), db.collection.updateMany(), or db.collection.replaceOne() includes upsert : true and no documents match the specified filter, then the operation creates a new document and inserts it. If there are matching documents, then the operation modifies or replaces the matching document or documents.
For details on the new document created, see the individual reference pages for the methods.
Example Collection
The examples on this page use the db.collection.find() method in the mongo shell. In the mongo shell, if the returned cursor is not assigned to a variable using the var keyword, then the cursor is automatically iterated up to 20 times to print up to the first 20 documents in the results.
To populate the users collection referenced in the examples, run the following in mongo shell:
NOTE: If the users collection already contains documents with the same _id values, you need to drop the collection (db.users.drop()) before inserting the example documents.
db.users.insertMany(
[
{
_id: 1,
name: "sue",
age: 19,
type: 1,
status: "P",
favorites: { artist: "Picasso", food: "pizza" },
finished: [ 17, 3 ],
badges: [ "blue", "black" ],
points: [
{ points: 85, bonus: 20 },
{ points: 85, bonus: 10 }
]
},
{
_id: 2,
name: "bob",
age: 42,
type: 1,
status: "A",
favorites: { artist: "Miro", food: "meringue" },
finished: [ 11, 25 ],
badges: [ "green" ],
points: [
{ points: 85, bonus: 20 },
{ points: 64, bonus: 12 }
]
},
{
_id: 3,
name: "ahn",
age: 22,
type: 2,
status: "A",
favorites: { artist: "Cassatt", food: "cake" },
finished: [ 6 ],
badges: [ "blue", "Picasso" ],
points: [
{ points: 81, bonus: 8 },
{ points: 55, bonus: 20 }
]
},
{
_id: 4,
name: "xi",
age: 34,
type: 2,
status: "D",
favorites: { artist: "Chagall", food: "chocolate" },
finished: [ 5, 11 ],
badges: [ "Picasso", "black" ],
points: [
{ points: 53, bonus: 15 },
{ points: 51, bonus: 15 }
]
},
{
_id: 5,
name: "xyz",
age: 23,
type: 2,
status: "D",
favorites: { artist: "Noguchi", food: "nougat" },
finished: [ 14, 6 ],
badges: [ "orange" ],
points: [
{ points: 71, bonus: 20 }
]
},
{
_id: 6,
name: "abc",
age: 43,
type: 1,
status: "A",
favorites: { food: "pizza", artist: "Picasso" },
finished: [ 18, 12 ],
badges: [ "black", "blue" ],
points: [
{ points: 78, bonus: 8 },
{ points: 57, bonus: 7 }
]
}
]
)