sh.splitAt()

Definition

sh.splitAt(namespace, query)

Splits a chunk at the shard key value specified by the query.

Important

mongosh Method

This page documents a mongosh method. This is not the documentation for database commands or language-specific drivers, such as Node.js.

For the database command, see the split command.

For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.

The method takes the following arguments:

Parameter	Type	Description
namespace	string	The namespace (i.e. <database>.<collection>) of the sharded collection that contains the chunk to split.
query	document	A query document that specifies the shard key value at which to split the chunk.

Compatibility

This method is available in deployments hosted in the following environments:

• MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

• MongoDB Enterprise: The subscription-based, self-managed version of MongoDB

• MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB

Consideration

In most circumstances, you should leave chunk splitting to the automated processes within MongoDB. However, when initially deploying a sharded cluster, it may be beneficial to pre-split manually an empty collection using methods such as sh.splitAt().

Behavior

sh.splitAt() splits the original chunk into two chunks. One chunk has a shard key range that starts with the original lower bound (inclusive) and ends at the specified shard key value (exclusive). The other chunk has a shard key range that starts with the specified shard key value (inclusive) as the lower bound and ends at the original upper bound (exclusive).

To split a chunk at its median point instead, see sh.splitFind().

Example

For the sharded collection test.foo, the following example splits a chunk at the shard key value x: 70.

sh.splitAt( "test.foo", { x: 70 } )