What is the _id Field in MongoDB?
- The
_id
field serves as the primary key for documents in a collection, ensuring each document has a unique identifier. - MongoDB guarantees that each
_id
value is unique within a collection. - If we don’t provide an
_id
field when inserting a document, MongoDB will automatically generate one for us . The default generation mechanism usesObjectId
.
- The most common type of
_id
value isObjectId
, which is a 12–byte identifier consisting of a timestamp, a random value, and an incrementing counter.
- While MongoDB provides automatic
_id
generation, we can also specify custom_id
values during document insertion, allowing us to use other data types such as strings or integers.
- The
_id
field is indexed by default, which can impact performance, especially when using custom_id
values or very large collections. - MongoDB provides efficient ways to query documents by their
_id
values, making it easy to retrieve specific document
How is id Generated in MongoDB
In MongoDB, each document stored in a collection is uniquely identified by a field called _id. This _id field serves as the primary key for the document and is important for ensuring document uniqueness and efficient retrieval. But have you ever wondered how these _id values are generated in MongoDB?
In this article, we’ll explore the Complexities of MongoDB ID generation by covering concepts, and examples to provide a comprehensive understanding.