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Set Missing Shard Key Fields

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  • Example

If you have missing shard key fields, you can set the shard key field to null. If you want to set the missing shard key field to a non-null value, see Change a Document's Shard Key Value.

To perform the update, you can use the following operations on a mongos

Command
Method
Description
update with
multi: true
  • Can be used to set the missing key value to null only.

  • Can be performed inside or outside a transaction.

  • Can be performed as a retryable write or not.

  • For additional requirements, refer to the specific command/method.

update with
multi: false
  • Can be used to set the missing key value to null or any other value.

  • The update to set missing shard key fields must meet one of the following requirements:

    • the filter of the query contains an equality condition on the full shard key in the query

    • the filter of the query contains an exact match on _id

    • the update targets a single shard

  • To set to a non-null value, refer to Change a Document's Shard Key Value.

  • For additional requirements, refer to the specific command/method.

  • Can be used to set the missing key value to null or any other value.

  • When setting missing shard key fields with a method that explicitly updates only one document, the update must meet one of the following requirements:

    • the filter of the query contains an equality condition on the full shard key in the query

    • the filter of the query contains an exact match on _id

    • the update targets a single shard

  • Missing key values are returned when matching on null. To avoid updating a key value that is null, include additional query conditions as appropriate.

  • To set to a non-null value, refer to Change a Document's Shard Key Value.

  • For additional requirements, refer to the specific command/method.

  • To set to a null value, you can specify multiple shard key modifications in the bulk operation.

  • When setting missing shard key fields with a method that explicitly updates only one document, the update must meet one of the following requirements:

    • the filter of the query contains an equality condition on the full shard key in the query

    • the filter of the query contains an exact match on _id

    • the update targets a single shard

  • To set to a non-null value, refer to Change a Document's Shard Key Value.

  • For additional requirements, refer to the underlying command/method.

Consider a sales collection which is sharded on the location field. Some documents in the collection have no location field. A missing field is considered the same as a null value for the field. To explicitly set these fields to null, run the following command:

db.sales.updateOne(
{ _id: 12345, location: null },
{ $set: { location: null } }
)

When setting missing shard key fields with db.collection.updateOne() or another method that explicitly updates only one document, the update must meet one of the following requirements:

  • the filter of the query contains an equality condition on the full shard key in the query

  • the filter of the query contains an exact match on _id

  • the update targets a single Shard

←  Change a Document's Shard Key ValueFind a Shard Key →

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