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Update Documents

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Update Documents in a Collection

Note

Starting in MongoDB 4.2, MongoDB can accept an aggregation pipeline to specify the modifications to make instead of an update document. See the method reference page for details.

Update a Single Document

Behavior

Atomicity

All write operations in MongoDB are atomic on the level of a single document. For more information on MongoDB and atomicity, see Atomicity and Transactions.

_id Field

Once set, you cannot update the value of the _id field nor can you replace an existing document with a replacement document that has a different _id field value.

Field Order

For write operations, MongoDB preserves the order of the document fields except for the following cases:

  • The _id field is always the first field in the document.

  • Updates that include renaming of field names may result in the reordering of fields in the document.

Write Acknowledgement

With write concerns, you can specify the level of acknowledgement requested from MongoDB for write operations. For details, see Write Concern.