Use Database Commands¶
The MongoDB command interface provides access to all non CRUD database operations. Fetching server stats, initializing a replica set, and running a map-reduce job are all accomplished with commands.
See Database Commands for list of all commands sorted by function.
Database Command Form¶
You specify a command first by constructing a standard BSON
document whose first key is the name of the command. For example,
specify the isMaster command using the following
BSON document:
{ isMaster: 1 }
Issue Commands¶
The mongo shell provides a helper method for running
commands called db.runCommand(). The following operation in
mongo runs the above command:
db.runCommand( { isMaster: 1 } )
Many drivers provide an equivalent for
the db.runCommand() method. Internally, running commands
with db.runCommand() is equivalent to a special query
against the $cmd collection.
Many common commands have their own shell helpers or wrappers in the
mongo shell and drivers, such as the
db.isMaster() method in the mongo JavaScript
shell.
You can use the maxTimeMS option to specify a time limit for the
execution of a command, see Terminate a Command for
more information on operation termination.
admin Database Commands¶
You must run some commands on the admin database. Normally, these operations resemble the followings:
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:
db.adminCommand( {buildInfo: 1} )
Command Responses¶
All commands return, at minimum, a document with an ok field
indicating whether the command has succeeded:
{ 'ok': 1 }
Failed commands return the ok field with a value of 0.