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sh.shardCollection(<namespace>, <key>) // Optional parameters omitted
For more information on the sharding method, see
Starting in version 4.4, documents in sharded collections can be
missing the shard key fields. A missing shard key falls into the
same range as a
null-valued shard key. See Missing Shard Key Fields.
In version 4.2 and earlier, shard key fields must exist in every document to be able to shard a sharded collection. To set missing shard key fields, see Set Missing Shard Key Fields.
Starting in MongoDB 4.2, you can update a document's shard key value
unless the shard key field is the immutable
_id field. In
MongoDB 4.2 and earlier, a document's shard key field value is
For details on updating the shard key value, see Change a Document's Shard Key Value.
Starting in MongoDB 5.0, you can reshard a collection by changing a document's shard key.
Starting in MongoDB 4.4, you can refine a shard key by adding a suffix field or fields to the existing shard key.
In MongoDB 4.2 and earlier, the choice of shard key cannot be changed after sharding.