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db.collection.update()

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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 3.6.

db.collection.update(
   <query>,
   <update>,
   {
     upsert: <boolean>,
     multi: <boolean>,
     writeConcern: <document>,
     collation: <document>,
     arrayFilters: [ <filterdocument1>, ... ]
   }
)

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.
collation document

Optional.

Specifies the collation to use for the operation.

Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks.

The collation option has the following syntax:

collation: {
   locale: <string>,
   caseLevel: <boolean>,
   caseFirst: <string>,
   strength: <int>,
   numericOrdering: <boolean>,
   alternate: <string>,
   maxVariable: <string>,
   backwards: <boolean>
}

When specifying collation, the locale field is mandatory; all other collation fields are optional. For descriptions of the fields, see Collation Document.

If the collation is unspecified but the collection has a default collation (see db.createCollection()), the operation uses the collation specified for the collection.

If no collation is specified for the collection or for the operations, MongoDB uses the simple binary comparison used in prior versions for string comparisons.

You cannot specify multiple collations for an operation. For example, you cannot specify different collations per field, or if performing a find with a sort, you cannot use one collation for the find and another for the sort.

New in version 3.4.
arrayFilters array

Optional. An array of filter documents that determines which array elements to modify for an update operation on an array field.

In the update document, use the $[<identifier>] filtered positional operator to define an identifier, which you then reference in the array filter documents. You cannot have an array filter document for an identifier if the identifier is not included in the update document.

Note

The <identifier> must begin with a lowercase letter and contain only alphanumeric characters.

You can include the same identifier multiple times in the update document; however, for each distinct identifier ($[identifier]) in the update document, you must specify exactly one corresponding array filter document. That is, you cannot specify multiple array filter documents for the same identifier. For example, if the update statement includes the identifier x (possibly multiple times), you cannot specify the following for arrayFilters that includes 2 separate filter documents for x:

[
  { "x.a": { $gt: 85 } },
  { "x.b": { $gt: 80 } }
]

However, you can specify compound conditions on the same identifier in a single filter document, such as in the following examples:

[
  { $or: [{"x.a": {$gt: 85}}, {"x.b": {$gt: 80}}] }
]

[
  { $and: [{"x.a": {$gt: 85}}, {"x.b": {$gt: 80}}] }
]

[
  { "x.a": { $gt: 85 }, "x.b": { $gt: 80 } }
]

For examples, see Specify arrayFilters for an Array Update Operations.

New in version 3.6.
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:

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 is a replacement document (i.e., contains only field and value pairs). If neither the <query> nor the <update> document specifies an _id field, MongoDB adds the _id field with an ObjectId value.
  • 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. Comparison operations from the <query> will not be included in the new document.

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