db.collection.findAndModify()¶

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Definition
Return Data
Behaviors
Examples

Definition¶

db.collection.findAndModify(<document>)¶

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.

The findAndModify() method has the following form:

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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:

Parameter	Type	Description
`query`	document	Optional. 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 select only one document to modify.
`sort`	document	Optional. Determines which document the operation modifies if the query selects multiple documents. `findAndModify()` modifies the first document in the sort order specified by this argument.
`remove`	Boolean	Must specify either the `remove` or the `update` field. Removes the document specified in the `query` field. Set this to `true` to remove the selected document . The default is `false`.
`update`	document	Must specify either the `remove` or the `update` field in the `findAndModify()` method. 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: `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`.

Return Data¶

The findAndModify() method returns either: the pre-modification document or, if new: true is set, the modified document.

Note

If the query finds no document for update or remove operations, findAndModify() returns null.
If the query finds no document for an upsert, operation, findAndModify() performs an insert. If 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 the query finds no document for an upsert, findAndModify() performs an insert. If new is false, and a sort option, the method returns an empty document {}.

Behaviors¶

Upsert and Unique Index¶

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.

In the following example, no document with the name Andy exists, and multiple clients issue the following command:

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

Then, if these clients’ findAndModify() 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.

Sharded Collections¶

When using findAndModify in a sharded environment, the query must contain the shard key for all operations against the shard cluster for the sharded collections.

findAndModify operations issued against mongos instances for non-sharded collections function normally.

Examples¶

Update and Return¶

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

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

This method performs the following actions:

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.
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.
The update increments the value of the score field by 1.
The method returns the original (i.e. pre-modification) document selected for this update:
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```
{
  "_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:
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```
null
```

Update and Insert¶

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

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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:

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{ }

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

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null

Update, Insert and Return New Document¶

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:

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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:

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

Sort and Remove¶

By including a sort specification on the rating field, the following example removes from the people collection a single document with the state value of active and the lowest rating among the matching documents:

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db.people.findAndModify(
   {
     query: { state: "active" },
     sort: { rating: 1 },
     remove: true
   }
)

The method returns the deleted document:

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{
   "_id" : ObjectId("52fba867ab5fdca1299674ad"),
   "name" : "XYZ123",
   "score" : 1,
   "state" : "active",
   "rating" : 3
}

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