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db.collection.findAndModify()

db.collection.findAndModify()

The findAndModify() method atomically modifies and returns a single document. By default, the returned document does not include the modifications made on the update. To return the document with the modifications made on the update, use the new option. The findAndModify() method is a shell helper around the findAndModify command.

db.collection.findAndModify( {
                               query: <document>,
                               sort: <document>,
                               remove: <boolean>,
                               update: <document>,
                               new: <boolean>,
                               fields: <document>,
                               upsert: <boolean>
                           } );

The db.collection.findAndModify() method takes a document parameter with the following subdocument fields:

Fields:
  • query (document) – Optional. Specifies the selection criteria for the modification. The query field employs the same query selectors as used in the db.collection.find() method. Although the query may match multiple documents, findAndModify() will only select one document to modify.
  • sort (document) – Optional. Determines which document the operation will modify if the query selects multiple documents. findAndModify() will modify the first document in the sort order specified by this argument.
  • remove (boolean) – Optional if update field exists. When true, removes the selected document. The default is false.
  • update (document) – Optional if remove field exists. Performs an update of the selected document. The update field employs the same update operators or field: value specifications to modify the selected document.
  • new (boolean) – Optional. When true, returns the modified document rather than the original. The findAndModify() method ignores the new option for remove operations. The default is false.
  • fields (document) –

    Optional. A subset of fields to return. The fields document specifies an inclusion of a field with 1, as in the following:

    fields: { <field1>: 1, <field2>: 1, ... }
    

    See projection.

  • upsert (boolean) – Optional. Used in conjunction with the update field. When true, findAndModify() creates a new document if the query returns no documents. The default is false.

The findAndModify() method returns either:

  • the pre-modification document or,
  • if the new: true option is set, the modified document.

Note

  • If no document is found for the update or remove, the method returns null.

  • If no document is found for an upsert, which means the command performs an insert, and new is false, and the sort option is NOT specified, the method returns null.

    Changed in version 2.2: Previously returned an empty document {}. See the 2.2 release notes for more information.

  • If no document is found for an upsert, which means the command performs an insert, and new is false, and a sort option is specified, the method returns an empty document {}.

Consider the following examples:

  • The following method updates an existing document in the people collection where the document matches the query criteria:

    db.people.findAndModify( {
        query: { name: "Tom", state: "active", rating: { $gt: 10 } },
        sort: { rating: 1 },
        update: { $inc: { score: 1 } }
    } )
    

    This method performs the following actions:

    1. The query finds a document in the people collection where the name field has the value Tom, the state field has the value active and the rating field has a value greater than 10.

    2. The sort orders the results of the query in ascending order. If multiple documents meet the query condition, the method will select for modification the first document as ordered by this sort.

    3. The update increments the value of the score field by 1.

    4. The method returns the original (i.e. pre-modification) document selected for this update:

      {
        "_id" : ObjectId("50f1e2c99beb36a0f45c6453"),
        "name" : "Tom",
        "state" : "active",
        "rating" : 100,
        "score" : 5
      }
      

      To return the modified document, add the new:true option to the method.

      If no document matched the query condition, the method returns null:

      null
      
  • The following method includes the upsert: true option to insert a new document if no document matches the query condition:

    db.people.findAndModify( {
        query: { name: "Gus", state: "active", rating: 100 },
        sort: { rating: 1 },
        update: { $inc: { score: 1 } },
        upsert: true
      } )
    

    If the method does not find a matching document, the method performs an upsert. Because the method included the sort option, it returns an empty document { } as the original (pre-modification) document:

    { }
    

    If the method did not include a sort option, the method returns null.

    null
    
  • The following method includes both the upsert: true option and the new:true option to return the newly inserted document if a document matching the query is not found:

    db.people.findAndModify( {
        query: { name: "Pascal", state: "active", rating: 25 },
        sort: { rating: 1 },
        update: { $inc: { score: 1 } },
        upsert: true,
        new: true
      }
    )
    

The method returns the newly inserted document:

{
  "_id" : ObjectId("50f49ad6444c11ac2448a5d6"),
  "name" : "Pascal",
  "rating" : 25,
  "score" : 1,
  "state" : "active"
}

When findAndModify() includes the upsert: true option and the query field(s) is not uniquely indexed, the method could insert a document multiple times in certain circumstances. For instance, if multiple clients each invoke the method with the same query condition and these methods complete the find phase before any of methods perform the modify phase, these methods could insert the same document.

Consider an example where no document with the name Andy exists and multiple clients issue the following command:

db.people.findAndModify(
                         {
                           query: { name: "Andy" },
                           sort: { rating: 1 },
                           update: { $inc: { score: 1 } },
                           upsert: true
                         }
                       )

If all the methods finish the query phase before any command starts the modify phase, and there is no unique index on the name field, the commands may all perform an upsert. To prevent this condition, create a unique index on the name field. With the unique index in place, the multiple methods would observe one of the following behaviors:

  • Exactly one findAndModify() would successfully insert a new document.
  • Zero or more findAndModify() methods would update the newly inserted document.
  • Zero or more findAndModify() methods would fail when they attempted to insert a duplicate. If the method fails due to a unique index constraint violation, you can retry the method. Absent a delete of the document, the retry should not fail.

Warning