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db.runCommand()

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  • Definition
  • Behavior
  • Examples
  • Response
db.runCommand(command, [options])

Provides a helper to run specified database commands. This is the preferred method to issue database commands, as it provides a consistent interface between the shell and drivers.

Parameter
Type
Description
command
document or string
Document or string that specifies the command. If specified as a string, db.runCommand() transforms the string into a document.
options
document
Starting in mongosh 2.0, options that specify how mongosh runs the command.

options.readPreference

Read preference to run the command with. If not specified, defaults to primary. db.runCommand() ignores any other read preference global configuration set, including using setReadPref() or by specifying readPreference in a connection string.

In mongosh 1.x, db.runCommand() does not take an options argument. To set the read preference, use Mongo.setReadPref() or specify readPreference in the connection string.

To specify a time limit in milliseconds, see Terminate Running Operations.

db.runCommand() runs the command in the context of the current database. Some commands are only applicable in the context of the admin database, and you must change your db object before running these commands or use db.adminCommand().

Starting in mongosh 2.0, you can specify the read preference for a command with the options argument. If you do not specify a read preference, db.runCommand() defaults to primary.

Warning

In mongosh 2.0, db.runCommand() ignores any other read preference global configuration set, including using Mongo.setReadPref() or by specifying readPreference in a connection string.

In mongosh 1.x, db.runCommand() does not take an options argument. db.runCommand() uses the read preference specified either by using Mongo.setReadPref() or by specifying readPreference in the connection string.

The following examples show how to use db.runCommand() to run database commands.

This example shows how to use db.runCommand() to run the hello command.

db.runCommand( { hello: 1 } )

For details on output, see hello Output.

For details on read preference behavior, see Read Preference.

This example shows how to use db.runCommand() to run the hello command with the secondaryPreferred read preference.

db.runCommand( { hello: 1 }, { readPreference: "secondaryPreferred" } )

For details on output, see hello Output.

For details on read preference behavior, see Read Preference.

The method returns a response document that contains the following fields:

Field
Description
<command result>
Result fields specific to the command that ran.
ok
A number that indicates if the command succeeded (1) or failed (0).
operationTime

The logical time of the operation. MongoDB uses the logical time to order operations. Only for replica sets and sharded clusters.

If the command does not generate an oplog entry, for example, a read operation, then the operation does not advance the logical clock. In this case, operationTime returns:

For operations associated with causally consistent sessions, the MongoDB drivers use the logical time to automatically set the Read Operations and afterClusterTime period.

$clusterTime

A document that returns the signed cluster time. Cluster time is a logical time used for ordering of operations. Only for replica sets and sharded clusters. For internal use only.

The document contains the following fields:

  • clusterTime: timestamp of the highest known cluster time for the member.

  • signature: a document that contains the hash of the cluster time and the id of the key used to sign the cluster time.

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