db.collection.update()¶

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Definition
Behavior
Examples
WriteResult
Additional Resources

Definition¶

db.collection.update(query, update, options)¶

Modifies an existing document or documents in a collection. The method can modify specific fields of an existing document or documents or replace an existing document entirely, depending on the update parameter.

By default, the update() method updates a single document. Set the Multi Parameter to update all documents that match the query criteria.

The update() method has the following form:

Changed in version 2.6.

db.collection.update(
   <query>,
   <update>,
   {
     upsert: <boolean>,
     multi: <boolean>,
     writeConcern: <document>
   }
)

The update() method takes the following parameters:

Parameter	Type	Description
`query`	document	The selection criteria for the update. The same query selectors as in the `find()` method are available. Changed in version 3.0: When you execute an `update()` with `upsert: true` and the query matches no existing document, MongoDB will refuse to insert a new document if the query specifies conditions on the `_id` field using dot notation. For more information and an example, see upsert:true with a Dotted _id Query.
`update`	document	The modifications to apply. For details see Update Parameter.
`upsert`	boolean	Optional. If set to `true`, creates a new document when no document matches the query criteria. The default value is `false`, which does not insert a new document when no match is found.
`multi`	boolean	Optional. If set to `true`, updates multiple documents that meet the `query` criteria. If set to `false`, updates one document. The default value is `false`. For additional information, see Multi Parameter.
`writeConcern`	document	Optional. A document expressing the write concern. Omit to use the default write concern. See Write Concern. New in version 2.6.

Changed in version 2.6: The update() method returns an object that contains the status of the operation.

Returns:	A WriteResult object that contains the status of the operation.

Behavior¶

Write Concern¶

Changed in version 2.6.

The update() method uses the update command, which uses the default write concern. To specify a different write concern, include the writeConcern option in the options parameter. See Override Default Write Concern for an example.

Update Parameter¶

The update() method either modifies specific fields in existing documents or replaces an existing document entirely.

Update Specific Fields¶

If the <update> document contains update operator modifiers, such as those using the $set modifier, then:

The <update> document must contain only update operator expressions.
The update() method updates only the corresponding fields in the document.

To update an embedded document or an array as a whole, specify the replacement value for the field. To update particular fields in an embedded document or in an array, use dot notation to specify the field.

Replace a Document Entirely¶

If the <update> document contains only field:value expressions, then:

The update() method replaces the matching document with the <update> document. The update() method does not replace the _id value. For an example, see Replace All Fields.
update() cannot update multiple documents.

Upsert Option¶

Upsert Behavior¶

If upsert is true and no document matches the query criteria, update() inserts a single document. The update creates the new document with either:

The fields and values of the <update> parameter if the <update> parameter contains only field and value pairs, or
The fields and values of both the <query> and <update> parameters if the <update> parameter contains update operator expressions. The update creates a base document from the equality clauses in the <query> parameter, and then applies the update expressions from the <update> parameter.

If upsert is true and there are documents that match the query criteria, update() performs an update.

See also

$setOnInsert

Use Unique Indexes¶

Warning

To avoid inserting the same document more than once, only use upsert: true if the query field is uniquely indexed.

Given a collection named people where no documents have a name field that holds the value Andy. Consider when multiple clients issue the following update with upsert: true at the same time:

db.people.update(
   { name: "Andy" },
   {
      name: "Andy",
      rating: 1,
      score: 1
   },
   { upsert: true }
)

If all update() operations complete the query portion before any client successfully inserts data, and there is no unique index on the name field, then each update operation may result in an insert.

To prevent MongoDB from inserting the same document more than once, create a unique index on the name field. With a unique index, if multiple applications issue the same update with upsert: true, exactly one update() would successfully insert a new document.

The remaining operations would either:

update the newly inserted document, or
fail when they attempted to insert a duplicate.

If the operation fails because of a duplicate index key error, applications may retry the operation which will succeed as an update operation.

`upsert:true` with a Dotted `_id` Query¶

When you execute an update() with upsert: true and the query matches no existing document, MongoDB will refuse to insert a new document if the query specifies conditions on the _id field using dot notation.

This restriction ensures that the order of fields embedded in the _id document is well-defined and not bound to the order specified in the query

If you attempt to insert a document in this way, MongoDB will raise an error.

For example, consider the following update operation. Since the update operation specifies upsert:true and the query specifies conditions on the _id field using dot notation, then the update will result in an error when constructing the document to insert.

db.collection.update( { "_id.name": "Robert Frost", "_id.uid": 0 },
   { "categories": ["poet", "playwright"] },
   { upsert: true } )

Multi Parameter¶

If multi is set to true, the update() method updates all documents that meet the <query> criteria. The multi update operation may interleave with other operations, both read and/or write operations. For unsharded collections, you can override this behavior with the $isolated operator, which isolates the update operation and disallows yielding during the operation. This isolates the update so that no client can see the updated documents until they are all processed, or an error stops the update operation.

If the <update> document contains only field:value expressions, then update() cannot update multiple documents.

For an example, see Update Multiple Documents.

Sharded Collections¶

All update() operations for a sharded collection that specify the multi: false option must include the shard key or the _id field in the query specification. update() operations specifying multi: false in a sharded collection without the shard key or the _id field return an error.

See also

findAndModify()

Examples¶

Update Specific Fields¶

To update specific fields in a document, use update operators in the <update> parameter.

For example, given a books collection with the following document:

{
  _id: 1,
  item: "TBD",
  stock: 0,
  info: { publisher: "1111", pages: 430 },
  tags: [ "technology", "computer" ],
  ratings: [ { by: "ijk", rating: 4 }, { by: "lmn", rating: 5 } ],
  reorder: false
}

The following operation uses:

the $inc operator to increment the stock field; and
the $set operator to replace the value of the item field, the publisher field in the info embedded document, the tags field, and the second element in the ratings array.

db.books.update(
   { _id: 1 },
   {
     $inc: { stock: 5 },
     $set: {
       item: "ABC123",
       "info.publisher": "2222",
       tags: [ "software" ],
       "ratings.1": { by: "xyz", rating: 3 }
     }
   }
)

The updated document is the following:

{
  "_id" : 1,
  "item" : "ABC123",
  "stock" : 5,
  "info" : { "publisher" : "2222", "pages" : 430 },
  "tags" : [ "software" ],
  "ratings" : [ { "by" : "ijk", "rating" : 4 }, { "by" : "xyz", "rating" : 3 } ],
  "reorder" : false
}

Remove Fields¶

The following operation uses the $unset operator to remove the tags field:

db.books.update( { _id: 1 }, { $unset: { tags: 1 } } )

See also

$unset, $rename, Update Operators

Replace All Fields¶

Given the following document in the books collection:

{
  _id: 2,
  item: "XYZ123",
  stock: 15,
  info: { publisher: "5555", pages: 150 },
  tags: [ ],
  ratings: [ { by: "xyz", rating: 5, comment: "ratings and reorder will go away after update"} ],
  reorder: false
}

The following operation passes an <update> document that contains only field and value pairs. The <update> document completely replaces the original document except for the _id field.

db.books.update(
   { item: "XYZ123" },
   {
     item: "XYZ123",
     stock: 10,
     info: { publisher: "2255", pages: 150 },
     tags: [ "baking", "cooking" ]
   }
)

The updated document contains only the fields from the replacement document and the _id field. That is, the fields ratings and reorder no longer exist in the updated document since the fields were not in the replacement document.

{
   "_id" : 2,
   "item" : "XYZ123",
   "stock" : 10,
   "info" : { "publisher" : "2255", "pages" : 150 },
   "tags" : [ "baking", "cooking" ]
}

Insert a New Document if No Match Exists¶

The following update sets the upsert option to true so that update() creates a new document in the books collection if no document matches the <query> parameter:

db.books.update(
   { item: "ZZZ135" },
   {
     item: "ZZZ135",
     stock: 5,
     tags: [ "database" ]
   },
   { upsert: true }
)

If no document matches the <query> parameter, the update operation inserts a document with only the fields and values of the <update> document and a new unique ObjectId for the _id field:

{
  "_id" : ObjectId("542310906694ce357ad2a1a9"),
  "item" : "ZZZ135",
  "stock" : 5,
  "tags" : [ "database" ]
}

For more information on upsert option and the inserted document, Upsert Option.

Update Multiple Documents¶

To update multiple documents, set the multi option to true. For example, the following operation updates all documents where stock is less than or equal to 10:

db.books.update(
   { stock: { $lte: 10 } },
   { $set: { reorder: true } },
   { multi: true }
)

If the reorder field does not exist in the matching document(s), the $set operator will add the field with the specified value. See $set for more information.

Override Default Write Concern¶

The following operation on a replica set specifies a write concern of "w: majority" with a wtimeout of 5000 milliseconds such that the method returns after the write propagates to a majority of the voting replica set members or the method times out after 5 seconds.

Changed in version 3.0: In previous versions, majority referred to the majority of all members of the replica set.

db.books.update(
   { stock: { $lte: 10 } },
   { $set: { reorder: true } },
   {
     multi: true,
     writeConcern: { w: "majority", wtimeout: 5000 }
   }
)

Combine the `upsert` and `multi` Options¶

Given a books collection that includes the following documents:

{
  _id: 5,
  item: "EFG222",
  stock: 18,
  info: { publisher: "0000", pages: 70 },
  reorder: true
}
{
  _id: 6,
  item: "EFG222",
  stock: 15,
  info: { publisher: "1111", pages: 72 },
  reorder: true
}

The following operation specifies both the multi option and the upsert option. If matching documents exist, the operation updates all matching documents. If no matching documents exist, the operation inserts a new document.

db.books.update(
   { item: "EFG222" },
   { $set: { reorder: false, tags: [ "literature", "translated" ] } },
   { upsert: true, multi: true }
)

The operation updates all matching documents and results in the following:

{
   "_id" : 5,
   "item" : "EFG222",
   "stock" : 18,
   "info" : { "publisher" : "0000", "pages" : 70 },
   "reorder" : false,
   "tags" : [ "literature", "translated" ]
}
{
   "_id" : 6,
   "item" : "EFG222",
   "stock" : 15,
   "info" : { "publisher" : "1111", "pages" : 72 },
   "reorder" : false,
   "tags" : [ "literature", "translated" ]
}

If the collection had no matching document, the operation would result in the insertion of a document using the fields from both the <query> and the <update> specifications:

{
   "_id" : ObjectId("5423200e6694ce357ad2a1ac"),
   "item" : "EFG222",
   "reorder" : false,
   "tags" : [ "literature", "translated" ]
}

For more information on upsert option and the inserted document, Upsert Option.

WriteResult¶

Changed in version 2.6.

Successful Results¶

The update() method returns a WriteResult object that contains the status of the operation. Upon success, the WriteResult object contains the number of documents that matched the query condition, the number of documents inserted by the update, and the number of documents modified:

WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

See

WriteResult.nMatched, WriteResult.nUpserted, WriteResult.nModified

Write Concern Errors¶

If the update() method encounters write concern errors, the results include the WriteResult.writeConcernError field:

WriteResult({
   "nMatched" : 1,
   "nUpserted" : 0,
   "nModified" : 1,
   "writeConcernError" : {
      "code" : 64,
      "errmsg" : "waiting for replication timed out at shard-a"
   }
})

See also

WriteResult.hasWriteConcernError()

Errors Unrelated to Write Concern¶

If the update() method encounters a non-write concern error, the results include the WriteResult.writeError field:

WriteResult({
   "nMatched" : 0,
   "nUpserted" : 0,
   "nModified" : 0,
   "writeError" : {
      "code" : 7,
      "errmsg" : "could not contact primary for replica set shard-a"
   }
})

See also

WriteResult.hasWriteError()

Additional Resources¶

Quick Reference Cards

← db.collection.totalIndexSize() db.collection.updateOne() →

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db.collection.update()¶

Definition¶

Behavior¶

Write Concern¶

Update Parameter¶

Update Specific Fields¶

Replace a Document Entirely¶

Upsert Option¶

Upsert Behavior¶

Use Unique Indexes¶

upsert:true with a Dotted _id Query¶

Multi Parameter¶

Sharded Collections¶

Examples¶

Update Specific Fields¶

Remove Fields¶

Replace All Fields¶

Insert a New Document if No Match Exists¶

Update Multiple Documents¶

Override Default Write Concern¶

Combine the upsert and multi Options¶

WriteResult¶

Successful Results¶

Write Concern Errors¶

Errors Unrelated to Write Concern¶

Additional Resources¶

`upsert:true` with a Dotted `_id` Query¶

Combine the `upsert` and `multi` Options¶