db.collection.unhideIndex.txt

===========================
db.collection.unhideIndex()
===========================

.. default-domain:: mongodb

.. contents:: On this page
   :local:
   :backlinks: none
   :depth: 1
   :class: singlecol

Definition
----------

.. method:: db.collection.unhideIndex()

   .. |dbcommand| replace:: ``index.hidden`` collection option set using the
      :dbcommand:`collMod` command
   .. include:: /includes/fact-mongosh-shell-method-alt

   Unhides an existing index from the query planner. Once unhidden, the
   indexes are immediately available for use.

Syntax
------

.. code-block:: javascript

   db.collection.unhideIndex(<index>)

Parameters
~~~~~~~~~~

The :method:`db.collection.unhideIndex()` method takes the following
parameter:

.. list-table::
   :header-rows: 1
   :widths: 20 20 80

   * - Parameter

     - Type

     - Description

   * - ``index``

     - string or document

     - Specifies the index to unhide from the query planner. You can
       specify the index either by the index name or by the index
       specification document.

       .. tip::

          You can use the :method:`db.collection.getIndexes()` method
          to find the index name or the index specification document.
       
       To unhide a :ref:`text <index-type-text>` index, specify the
       index name.

The :method:`db.collection.unhideIndex()` is a :binary:`mongosh` shell
wrapper for the :dbcommand:`collMod` command.

Behavior
--------

Index Modifications Reset Statistics
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Unhiding a hidden index resets its :pipeline:`$indexStats`.

No-op
~~~~~

Unhiding an already unhidden index has no effect on the index. However,
the operation will still generate an empty oplog entry.

Required Access
---------------

If the deployment enforces authentication/authorization, you must have
the :authaction:`collMod` privilege in the collection's database.

The built-in role :authrole:`dbAdmin` provides the required privileges.

Example
-------

The following example unhides an existing index.

First, use :method:`db.collection.createIndex()` to create a hidden
index:

.. code-block:: javascript

   db.restaurants.createIndex( { borough: 1, ratings: 1 }, { hidden: true } );

To verify, run :method:`db.collection.getIndexes()` on the
``restaurants`` collection:

.. code-block:: javascript

   db.restaurants.getIndexes();

The operation returns the following information:

.. code-block:: javascript
   :emphasize-lines: 6

   [
      {
         "v" : 2,
         "key" : {
            "_id" : 1
         },
         "name" : "_id_"
      },
      {
         "v" : 2,
         "key" : {
            "borough" : 1,
            "ratings" : 1
         },
         "name" : "borough_1_ratings_1",
         "hidden" : true
      }
   ]

The index option ``hidden`` is only returned if the value is ``true``.

To unhide the index, you can specify either the index key specification
document or the index name to the :method:`db.collection.unhideIndex()`
method. The following specifies the index name:

.. code-block:: javascript

   db.restaurants.unhideIndex( "borough_1_ratings_1" );  

To verify, run :method:`db.collection.getIndexes()` on the
``restaurants`` collection:

.. code-block:: javascript

   db.restaurants.getIndexes()

The operation returns the following information:

.. code-block:: javascript

   [
      {
         "v" : 2,
         "key" : {
            "_id" : 1
         },
         "name" : "_id_"
      },
      {
         "v" : 2,
         "key" : {
            "borough" : 1,
            "ratings" : 1
         },
         "name" : "borough_1_ratings_1"
      }
   ]

The index option ``hidden`` no longer appears as part of the
``borough_1_ratings_1`` index since the field is only returned if the
value is ``true``.

.. seealso::

   - :method:`db.collection.hideIndex()`
   - :ref:`db.collection.createIndex() <method-createIndex-hidden>`