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update.txt
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================
Update Operators
================
.. default-domain:: mongodb
.. contents:: On this page
:local:
:backlinks: none
:depth: 1
:class: singlecol
.. _update-operators-top-level:
The following modifiers are available for use in update operations;
e.g. in :method:`db.collection.update()` and
:method:`db.collection.findAndModify()`.
Specify the operator expression in a document of the form:
.. code-block:: javascript
{
<operator1>: { <field1>: <value1>, ... },
<operator2>: { <field2>: <value2>, ... },
...
}
.. include:: /includes/extracts/operators-toc-explanation.rst
.. _update-operators:
Update Operators
----------------
Fields
~~~~~~
.. only:: website
.. list-table::
:widths: 30,70
:header-rows: 1
* - Name
- Description
* - :update:`$currentDate`
- Sets the value of a field to current date, either as a Date or a Timestamp.
* - :update:`$inc`
- Increments the value of the field by the specified amount.
* - :update:`$min`
- Only updates the field if the specified value is less than the existing field value.
* - :update:`$max`
- Only updates the field if the specified value is greater than the existing field value.
* - :update:`$mul`
- Multiplies the value of the field by the specified amount.
* - :update:`$rename`
- Renames a field.
* - :update:`$set`
- Sets the value of a field in a document.
* - :update:`$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.
* - :update:`$unset`
- Removes the specified field from a document.
.. toctree::
:titlesonly:
:hidden:
/reference/operator/update-field
Array
~~~~~
Operators
`````````
.. list-table::
:widths: 30,70
:header-rows: 1
* - Name
- Description
* - :update:`$`
- Acts as a placeholder to update the first element that matches the query condition.
* - :update:`$[]`
- Acts as a placeholder to update all elements in an array for the documents that match the query condition.
* - :update:`$[\<identifier\>]`
- Acts as a placeholder to update all elements that match the ``arrayFilters`` condition for the documents that match the query condition.
* - :update:`$addToSet`
- Adds elements to an array only if they do not already exist in the set.
* - :update:`$pop`
- Removes the first or last item of an array.
* - :update:`$pull`
- Removes all array elements that match a specified query.
* - :update:`$push`
- Adds an item to an array.
* - :update:`$pullAll`
- Removes all matching values from an array.
Modifiers
`````````
.. list-table::
:widths: 30,70
:header-rows: 1
* - Name
- Description
* - :update:`$each`
- Modifies the :update:`$push` and :update:`$addToSet` operators to append multiple items for array updates.
* - :update:`$position`
- Modifies the :update:`$push` operator to specify the position in the array to add elements.
* - :update:`$slice`
- Modifies the :update:`$push` operator to limit the size of updated arrays.
* - :update:`$sort`
- Modifies the :update:`$push` operator to reorder documents stored in an array.
.. toctree::
:titlesonly:
:hidden:
/reference/operator/update-array
Bitwise
~~~~~~~
.. list-table::
:widths: 30,70
:header-rows: 1
* - Name
- Description
* - :update:`$bit`
- Performs bitwise ``AND``, ``OR``, and ``XOR`` updates of integer values.
.. toctree::
:titlesonly:
:hidden:
/reference/operator/update-bitwise