OPTIONS

db.collection.update()

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. Use the same query selectors as used in the find() method.
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 Safe Writes.

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

Safe Writes

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. For an example, see Update Specific Fields.

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 Parameter

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, or
  • The fields and values of both the <query> and <update> parameters if the <update> parameter contains only 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.

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 an upsert parameter 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 an applications issues a group of upsert operations, 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.

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. If the <update> parameter refers to non-existent fields in the current document, the update() method adds the fields to the document.

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

{ "_id" : 11, "item" : "Divine Comedy", "stock" : 2 }

The following operation adds a price field to the document and increments the stock field by 5.

db.books.update(
   { item: "Divine Comedy" },
   {
      $set: { price: 18 },
      $inc: { stock: 5 }
   }
)

The updated document is now the following:

{ "_id" : 11, "item" : "Divine Comedy", "price" : 18, "stock" : 7 }

Update Specific Fields in Embedded Documents

Use dot notation to update specific fields in embedded documents.

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

{ _id: 50, item: "TDB", stock: 0, isbn: { group: 11, publisher: 1111, title: 11, digit: 1 } }

The following example updates the publisher field and the digit field in the isbn embedded document:

db.books.update(
   { _id: 50 },
   { $set: { "isbn.publisher": 2222, "isbn.digit": 0 } }
)

Remove Fields

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

db.books.update( { _id: 11 }, { $unset: { stock: 1 } } )

Replace All Fields

Given the following document in the books collection:

{
    "_id" : 22,
    "item" : "The Banquet",
    "author" : "Dante",
    "price" : 20,
    "stock" : 4
}

The following operation passes an <update> document that contains only field and value pairs, which means the document replaces all the fields in the original document. The operation does not replace the _id value. The operation contains the same value for the item field in both the <query> and <update> documents, which means the field does not change:

db.books.update(
   { item: "The Banquet" },
   { item: "The Banquet", price: 19 , stock: 3 }
)

The operation creates the following new document. The operation removed the author field and changed the values of the price and stock fields:

{
    "_id" : 22,
    "item" : "The Banquet",
    "price" : 19,
    "stock" : 3
}

Insert a New Document if No Match Exists (Upsert)

The following command 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: "The New Life" },
   { item: "The New Life", author: "Dante", price: 15 },
   { upsert: true }
)

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

{
    "_id" : ObjectId("51e5990c95098ed69d4a89f2"),
    "author" : "Dante",
    "item" : "The New Life",
    "price" : 15
}

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 5:

db.books.update(
   { stock: { $lt: 5 } },
   { $set: { reorder: true } },
   { multi: true }
)

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 replica set members or the method times out after 5 seconds.

db.books.update(
   { stock: { $lt: 5 } },
   { $set: { reorder: true } },
   {
     multi: true,
     writeConcern: { w: "majority", wtimeout: 5000 }
   }
)

Combine the Upsert and Multi Parameters

Given a books collection that includes the following documents:

{ _id: 11, author: "Dante", item: "Divine Comedy", price: 18, translatedBy: "abc123" }
{ _id: 12, author: "Dante", item: "Divine Comedy", price: 21, translatedBy: "jkl123" }
{ _id: 13, author: "Dante", item: "Divine Comedy", price: 15, translatedBy: "xyz123" }

The following command specifies the multi parameter to update all documents where item is "Divine Comedy" and the author is "Dante" and specifies the upsert parameter to create a new document if no matching documents are found:

db.books.update(
   { item: "Divine Comedy", author: "Dante" },
   { $set: { reorder: false, price: 10 } },
   { upsert: true, multi: true }
)

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

{ _id: 11, author: "Dante", item: "Divine Comedy", price: 10, translatedBy: "abc123", reorder: false }
{ _id: 12, author: "Dante", item: "Divine Comedy", price: 10, translatedBy: "jkl123", reorder: false }
{ _id: 13, author: "Dante", item: "Divine Comedy", price: 10, translatedBy: "xyz123", reorder: false }

If the collection had no matching document, the operation would result in the insertion of a document:

{ _id: ObjectId("536aa66422363a21bc16bfd7"), author: "Dante", item: "Divine Comedy", reorder: false, price: 10 }

Update Arrays

Update an Element by Position

If the update operation requires an update of an element in an array field, the update() method can perform the update using the position of the element and dot notation. Arrays in MongoDB are zero-based.

The following operation queries the bios collection for the first document with the _id field equal to 1 and updates the second element in the contribs array:

db.bios.update(
   { _id: 1 },
   { $set: { "contribs.1": "ALGOL 58" } }
)

Update an Element if Position is Unknown

If the position in the array is not known, the update() method can perform the update using the $ positional operator. The array field must appear in the <query> parameter in order to determine which array element to update.

The following operation queries the bios collection for the first document where the _id field equals 3 and the contribs array contains an element equal to compiler. If found, the update() method updates the first matching element in the array to A compiler in the document:

db.bios.update(
   { _id: 3, "contribs": "compiler" },
   { $set: { "contribs.$": "A compiler" } }
)

Update a Document Element

The update() method can perform the update of an array that contains embedded documents by using the positional operator (i.e. $) and the dot notation.

The following example queries the bios collection for the first document where the _id field equals 4 and the awards array contains an embedded document where the by field equals ACM. If found, the update() method updates the by field in the first matching embeddocument:

db.bios.update(
   { _id: 4, "awards.by": "ACM"  } ,
   { $set: { "awards.$.by": "Association for Computing Machinery" } }
)

Add an Element

The following operation queries the bios collection for the first document that has an _id field equal to 1 and adds a new element to the awards field:

db.bios.update(
   { _id: 1 },
   {
     $push: { awards: { award: "IBM Fellow", year: 1963, by: "IBM" } }
   }
)

In the next example, the $set operator uses dot notation to access the middle field in the name embedded document. The $push operator adds an embedded document to the awards array.

Consider the following operation:

db.bios.update(
   { _id: 1 },
   {
      $set: { "name.middle": "Warner" },
      $push: { awards: {
         award: "IBM Fellow",
            year: "1963",
            by: "IBM"
         }
      }
   }
)

This update() operation:

  • Modifies the field name whose value is another document. Specifically, the $set operator updates the middle field in the name document. The document uses dot notation to access a field in an embedded document.
  • Adds an element to the field awards, whose value is an array. Specifically, the $push operator adds another document as an element to the field awards.

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 via an upsert, and the number of documents modified:

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

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"
   }
})

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"
   }
})