Refine a Shard Key

New in version 4.4.

Refining a collection's shard key allows for a more fine-grained data distribution and can address situations where the existing key has led to jumbo chunks due to insufficient cardinality.


Starting in MongoDB 5.0, you can also reshard your collection by providing a new shard key for the collection.

To refine a collection's shard key, use the refineCollectionShardKey command. The refineCollectionShardKey adds a suffix field or fields to the existing key to create the new shard key.

For example, you may have an existing orders collection in a test database with the shard key { customer_id: 1 }. You can use the refineCollectionShardKey command to change the shard key to the new shard key { customer_id: 1, order_id: 1 }:

db.adminCommand( {
refineCollectionShardKey: "test.orders",
key: { customer_id: 1, order_id: 1 }
} )
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