use-database-commands.txt

:orphan:

=====================
Use Database Commands
=====================

.. default-domain:: mongodb

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The MongoDB command interface provides access to all :term:`non CRUD
<crud>` database operations. Fetching server stats, initializing a
replica set, and running a map-reduce job are all accomplished with
commands.

See :doc:`/reference/command` for list of all commands sorted by
function.

Database Command Form
---------------------

You specify a command first by constructing a standard :term:`BSON`
document whose first key is the name of the command. For example,
specify the :dbcommand:`hello` command using the following
:term:`BSON` document:

.. code-block:: javascript

   { hello: 1 }

.. _issue-commands:

Issue Commands
--------------

The :binary:`~bin.mongo` shell provides a helper method for running
commands called :method:`db.runCommand()`. The following operation in
:binary:`~bin.mongo` runs the above command:

.. code-block:: javascript

   db.runCommand( { hello: 1 } )

Many :ecosystem:`drivers </drivers>` provide an equivalent for
the :method:`db.runCommand()` method. Internally, running commands
with :method:`db.runCommand()` is equivalent to a special query
against the :term:`$cmd` collection.

Many common commands have their own shell helpers or wrappers in the
:binary:`~bin.mongo` shell and drivers, such as the
:method:`db.hello()` method in the :binary:`~bin.mongo` JavaScript
shell.

You can use the ``maxTimeMS`` option to specify a time limit for the
execution of a command, see :ref:`terminate-long-running-commands` for
more information on operation termination.

.. _admin-command:

``admin`` Database Commands
---------------------------

You must run some commands on the :term:`admin database`. Normally,
these operations resemble the followings:

.. code-block:: javascript

   use admin
   db.runCommand( {buildInfo: 1} )

However, there's also a command helper that automatically runs the
command in the context of the ``admin`` database:

.. code-block:: javascript

   db.adminCommand( {buildInfo: 1} )

Command Responses
-----------------

For all commands, MongoDB returns a response document that contains the
following fields:

.. include:: /includes/fact-runCommand-results.rst