Update Documents

mongo --host 127.0.0.1:27017

The examples on this page use the inventory collection. To create and/or populate the inventory collection, run the following:

db.inventory.deleteMany({})
{ "acknowledged" : true, "deletedCount" : 5 }

db.inventory.insertMany( [
   { item: "canvas", qty: 100, size: { h: 28, w: 35.5, uom: "cm" }, status: "A" },
   { item: "journal", qty: 25, size: { h: 14, w: 21, uom: "cm" }, status: "A" },
   { item: "mat", qty: 85, size: { h: 27.9, w: 35.5, uom: "cm" }, status: "A" },
   { item: "mousepad", qty: 25, size: { h: 19, w: 22.85, uom: "cm" }, status: "P" },
   { item: "notebook", qty: 50, size: { h: 8.5, w: 11, uom: "in" }, status: "P" },
   { item: "paper", qty: 100, size: { h: 8.5, w: 11, uom: "in" }, status: "D" },
   { item: "planner", qty: 75, size: { h: 22.85, w: 30, uom: "cm" }, status: "D" },
   { item: "postcard", qty: 45, size: { h: 10, w: 15.25, uom: "cm" }, status: "A" },
   { item: "sketchbook", qty: 80, size: { h: 14, w: 21, uom: "cm" }, status: "A" },
   { item: "sketch pad", qty: 95, size: { h: 22.85, w: 30.5, uom: "cm" }, status: "A" }
] );
{
        "acknowledged" : true,
        "insertedIds" : [
                ObjectId("5b56ce42e68eb0362ce719b2"),
                ObjectId("5b56ce42e68eb0362ce719b3"),
                ObjectId("5b56ce42e68eb0362ce719b4"),
                ObjectId("5b56ce42e68eb0362ce719b5"),
                ObjectId("5b56ce42e68eb0362ce719b6"),
                ObjectId("5b56ce42e68eb0362ce719b7"),
                ObjectId("5b56ce42e68eb0362ce719b8"),
                ObjectId("5b56ce42e68eb0362ce719b9"),
                ObjectId("5b56ce42e68eb0362ce719ba"),
                ObjectId("5b56ce42e68eb0362ce719bb")
        ]
}

Update Documents in a Collection

To update a document, MongoDB provides update operators, such as $set, to modify field values.

Update Methods

Update a Single Document

The following example uses the db.collection.updateOne() method on the inventory collection to update the first document where item equals "paper":

db.inventory.updateOne(
   { item: "paper" },
   {
     $set: { "size.uom": "cm", status: "P" },
     $currentDate: { lastModified: true }
   }
)
{ "acknowledged" : true, "matchedCount" : 1, "modifiedCount" : 1 }

The update operation:

• uses the $set operator to update the value of the size.uom field to "cm" and the value of the status field to "P",
• uses the $currentDate operator to update the value of the lastModified field to the current date. If lastModified field does not exist, $currentDate will create the field.

Update Multiple documents

The following example uses the db.collection.updateMany() method on the inventory collection to update all documents where qty is less than 50:

db.inventory.updateMany(
   { "qty": { $lt: 50 } },
   {
     $set: { "size.uom": "in", status: "P" },
     $currentDate: { lastModified: true }
   }
)
{ "acknowledged" : true, "matchedCount" : 3, "modifiedCount" : 3 }

Replace a Document

To replace the entire content of a document except for the _id field, pass an entirely new document as the second argument to db.collection.replaceOne().

When replacing a document, the replacement document must consist of only field/value pairs; i.e. do not include update operators expressions.

_id field is immutable; however, if you do include the _id field, it must have the same value as the current value.

The following example replaces the first document from the inventory collection where item: "paper":

db.inventory.replaceOne(
   { item: "paper" },
   { item: "paper", instock: [ { warehouse: "A", qty: 60 }, { warehouse: "B", qty: 40 } ] }
)
{ "acknowledged" : true, "matchedCount" : 1, "modifiedCount" : 1 }

db.inventory.find( {} )
{ "_id" : ObjectId("5b56ce42e68eb0362ce719b2"), "item" : "canvas", "qty" : 100, "size" : { "h" : 28, "w" : 35.5, "uom" : "cm" }, "status" : "A" }
{ "_id" : ObjectId("5b56ce42e68eb0362ce719b3"), "item" : "journal", "qty" : 25, "size" : { "h" : 14, "w" : 21, "uom" : "in" }, "status" : "P", "lastModified" : ISODate("2018-07-24T07:02:47.805Z") }
{ "_id" : ObjectId("5b56ce42e68eb0362ce719b4"), "item" : "mat", "qty" : 85, "size" : { "h" : 27.9, "w" : 35.5, "uom" : "cm" }, "status" : "A" }
{ "_id" : ObjectId("5b56ce42e68eb0362ce719b5"), "item" : "mousepad", "qty" : 25, "size" : { "h" : 19, "w" : 22.85, "uom" : "in" }, "status" : "P", "lastModified" : ISODate("2018-07-24T07:02:47.806Z") }
{ "_id" : ObjectId("5b56ce42e68eb0362ce719b6"), "item" : "notebook", "qty" : 50, "size" : { "h" : 8.5, "w" : 11, "uom" : "in" }, "status" : "P" }
{ "_id" : ObjectId("5b56ce42e68eb0362ce719b7"), "item" : "paper", "instock" : [ { "warehouse" : "A", "qty" : 60 }, { "warehouse" : "B", "qty" : 40 } ] }
{ "_id" : ObjectId("5b56ce42e68eb0362ce719b8"), "item" : "planner", "qty" : 75, "size" : { "h" : 22.85, "w" : 30, "uom" : "cm" }, "status" : "D" }
{ "_id" : ObjectId("5b56ce42e68eb0362ce719b9"), "item" : "postcard", "qty" : 45, "size" : { "h" : 10, "w" : 15.25, "uom" : "in" }, "status" : "P", "lastModified" : ISODate("2018-07-24T07:02:47.806Z") }
{ "_id" : ObjectId("5b56ce42e68eb0362ce719ba"), "item" : "sketchbook", "qty" : 80, "size" : { "h" : 14, "w" : 21, "uom" : "cm" }, "status" : "A" }
{ "_id" : ObjectId("5b56ce42e68eb0362ce719bb"), "item" : "sketch pad", "qty" : 95, "size" : { "h" : 22.85, "w" : 30.5, "uom" : "cm" }, "status" : "A" }

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.

Document Size

When performing update operations that increase the document size beyond the allocated space for that document, the update operation relocates the document on disk.

Field Order

MongoDB preserves the order of the document fields following write operations 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.

Upsert Option

If updateOne(), updateMany(), or replaceOne() includes upsert : true and no documents match the specified filter, then the operation creates a new document and inserts it. If there are matching documents, then the operation modifies or replaces the matching document or documents.

Write Acknowledgement

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