enableSharding¶

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Definition
Syntax
Behavior
Example

Definition¶

enableSharding¶: The enableSharding command enables sharding on the specified database. Once you enabled sharding for a database, you can use the shardCollection command to shard collections in that database.

Tip

In the mongo Shell, this command can also be run through the sh.enableSharding helper method.

Helper methods are convenient for mongo users, but they may not return the same level of information as database commands. In cases where the convenience is not needed or the additional return fields are required, use the database command.

Syntax¶

The enableSharding command has the following syntax:

Recommended. Specify just the database for which to enable sharding.
copy
```
db.adminCommand( {
   enableSharding: "<database name>"
} )
```

Optionally, starting in MongoDB 4.2.2 (and 4.0.14), you can include the primary shard specification in the command, although this is not recommended:

copy

db.adminCommand( {
   enableSharding: "<database name>",
   primaryShard: "<shard name>"  // Available starting in MongoDB 4.2.2 (and 4.0.14)
} )

You can only run enableSharding in the admin database from a mongos instance.

Fields¶

The command takes the following fields:

Field

Type

Description

enableSharding

String

The database for which you wish to enable sharding.

primaryShard

String

Optional. The primary shard for the database; the primary shard contains the unsharded collection for this database. In general, rather than explicitly specifying the primary shard, it is recommended to let the balancer select the primary shard instead.

Tip

In general, you should not need to specify the primary shard. Allow the balancer to select the primary shard instead.

Available starting in MongoDB 4.2.2 (and 4.0.14)

Returns¶

The command returns a document that contains status of the operation.

Behavior¶

Write Concern¶

mongos uses "majority" for the enableSharding command and its helper sh.enableSharding().

Primary Shard¶

In general, you should not need to specify the primaryShard in the command. Instead, allow the balancer to select the primary shard.

However, if you do specify the primaryShard in the command for a database and the database is already sharding enabled with a different primary shard, the operation returns an error and the primary shard for the database remains as before. To change the primary shard for a database, use movePrimary instead.

Example¶

The following command, run from a mongos, enables sharding for the test database:

copy

db.adminCommand( { enableSharding: "test" } )

To verify, run sh.status().