Each chain represents and designates a specific aspect of the document's identity. How Does MongoDB ObjectID Work?Architecturally, by default the _id field is an ObjectID, one of MongoDB's BSON types. The following values make up the full 12-byte combination of every _ID ( quoted from MongoDB's documentation): The ObjectID is the primary key for the stored document and is automatically generated when creating a new document in a collection. _id is the primary key on elements in a collection with it, records can be differentiated by default.These are also a few _id field principal characteristics you should know about: a 2-byte process id, and a 3-byte counter, starting with a random value."."a 4-byte value representing the seconds since the Unix epoch. Users can also override _id to something other than an ObjectID data type, if desired.Lookups specifying refer to the _id index as their guide. Is MongoDB ObjectID Unique? According to MongoDB, ObjectID can be considered globally unique. The first nine bytes in a MongoDB _ID guarantee its uniqueness across machines and processes, in relation to a single second the last three bytes provide uniqueness within a single second in a single process.Īre There Any Fields All Documents in MongoDB Must Have? All documents in MongoDB must have a populated _id field. If a document hasn’t been assigned an _id value, MongoDB will automatically generate one. Important MongoDB Commands for ObjectIDThanks to the universal, required nature of the _id field, there are several actions available to users to simplify your organization and handling of documents.
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