Why does MongoDB use _id?

Every document in the collection has an “_id” field that is used to uniquely identify the document in a particular collection it acts as the primary key for the documents in the collection.

How does the value of _id get assigned to a document?

_id is the primary key on documents in a collection; with it, documents (records) can be differentiated from each one another. _id is automatically indexed. Lookups specifying { _id: } refer to the _id index as their guide. By default the _id field is of type ObjectID, one of MongoDB’s BSON types.

How does MongoDB generate _id?

ObjectID is automatically generated by the database drivers, and will be assigned to the _id field of each document. ObjectID can be considered globally unique for all practical purposes. ObjectID encodes the timestamp of its creation time, which may be used for queries or to sort by creation time.

Can we set _id in MongoDB?

_id field is reserved for primary key in mongodb, and that should be a unique value. If you don’t set anything to _id it will automatically fill it with “MongoDB Id Object”. But you can put any unique info into that field.

What is difference between id and _ID in MongoDB?

The _id field in MongoDB document database is considered to be the default field for BSON ObjectId’s and it is, by default, indexed. _id and id are not the same. You may also prefer to add a field called id if you want, but it will not be index unless you add an index.

What is _ID field in MongoDB?

Architecturally, by default the _id field is an ObjectID, one of MongoDB’s BSON types. The ObjectID is the primary key for the stored document and is automatically generated when creating a new document in a collection.

Can we hide _ID in MongoDB?

The _id field is always included by default. To exclude the _id field from the output documents of the $project stage, specify the exclusion of the _id field by setting it to 0 in the projection document.

How does the value of _ID get assigned to a document MongoDB?

In MongoDB, each document stored in a collection requires a unique _id field that acts as a primary key. If an inserted document omits the _id field, the MongoDB driver automatically generates an ObjectId for the _id field.

How does the value of _id get assigned to a document MongoDB?

What is _id in MongoDB?

_id is the primary key on elements in a collection; with it, records can be differentiated by default. _id is automatically indexed. Lookups specifying { _id: } refer to the _id index as their guide. Users can also override _id to something other than an ObjectID data type, if desired.

How do you omit the _ID from the projection?

To exclude the _id field from the output documents of the $project stage, specify the exclusion of the _id field by setting it to 0 in the projection document.