Update Operators¶

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Update Operators

The following modifiers are available for use in update operations, for example, in db.collection.updateMany() and db.collection.findAndModify().

Specify the operator expression in a document of the form:

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{
   <operator1>: { <field1>: <value1>, ... },
   <operator2>: { <field2>: <value2>, ... },
   ...
}

Note

For details on specific operator, including syntax and examples, click on the specific operator to go to its reference page.

Update Operators¶

Behavior¶

Starting in MongoDB 5.0, update operators process document fields with string-based names in lexicographic order. Fields with numeric names are processed in numeric order.

In MongoDB 4.4 and earlier, update operators process all document fields in lexicographic order.

Consider this example $set command:

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{ $set: { "a.2": <new value>, "a.10": <new value>, } }

In MongoDB 5.0 and later, "a.2" is processed before "a.10" because 2 comes before 10 in numeric order.

In MongoDB 4.4 and earlier, "a.10" is processed before "a.2" because 10 comes before 2 in lexicographic order.

Fields¶

Name	Description
`$currentDate`	Sets the value of a field to current date, either as a Date or a Timestamp.
`$inc`	Increments the value of the field by the specified amount.
`$min`	Only updates the field if the specified value is less than the existing field value.
`$max`	Only updates the field if the specified value is greater than the existing field value.
`$mul`	Multiplies the value of the field by the specified amount.
`$rename`	Renames a field.
`$set`	Sets the value of a field in a document.
`$setOnInsert`	Sets the value of a field if an update results in an insert of a document. Has no effect on update operations that modify existing documents.
`$unset`	Removes the specified field from a document.

Array¶

Operators¶

Name	Description
`$`	Acts as a placeholder to update the first element that matches the query condition.
`$[]`	Acts as a placeholder to update all elements in an array for the documents that match the query condition.
`$[<identifier>]`	Acts as a placeholder to update all elements that match the `arrayFilters` condition for the documents that match the query condition.
`$addToSet`	Adds elements to an array only if they do not already exist in the set.
`$pop`	Removes the first or last item of an array.
`$pull`	Removes all array elements that match a specified query.
`$push`	Adds an item to an array.
`$pullAll`	Removes all matching values from an array.

Modifiers¶

Name	Description
`$each`	Modifies the `$push` and `$addToSet` operators to append multiple items for array updates.
`$position`	Modifies the `$push` operator to specify the position in the array to add elements.
`$slice`	Modifies the `$push` operator to limit the size of updated arrays.
`$sort`	Modifies the `$push` operator to reorder documents stored in an array.

Bitwise¶

Name	Description
`$bit`	Performs bitwise `AND`, `OR`, and `XOR` updates of integer values.

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