What is ObjectId in MongoDB
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. “_id” field can be used in any format and the default format is ObjectId of the document.
An ObjectID is a 12-byte Field Of BSON type
- The first 4 bytes representing the Unix Timestamp of the document
- The next 3 bytes are the machine Id on which the MongoDB server is running.
- The next 2 bytes are of process id
- The last Field is 3 bytes used for increment the objectid.
Format of ObjectId:
ObjectId(<hexadecimal>)
ObjectId accepts one parameter which is optional Hexadecimal ObjectId in String.
We can give our own ObjectId to the document but it must be unique.
*db.<collectionname>.insertOne({"_id":"231231"})
Example:
Database : gfg
Collection: student_gfg
Methods of ObjectId:
- str: Returns the hexadecimal string format of the ObjectId
- ObjectId.getTimestamp() : It returns the timestamp portion of the object as a Date.
- ObjectId.valueOf(): It return the hexadecimal format of a given String Literal.
- ObjectId.toString(): This method returns ObjectId in String format in javascript representation.
1.Creating ObjectId: To generate new ObjectId of particular document.
newObjectId = ObjectId()
Output:
ObjectId(“5f92cbf10cf217478ba93561”)
2.Timestamp of the ObjectID: It returns the timestamp information of the object as a Date in ISO format.
var id =new ObjectId();
id.getTimestamp()
Output:
ISODate(“2020-10-23T12:32:42Z”)
3.Converting ObjectId to string: ObjectId can be converted into string format.
new ObjectId().str
Output:
5f92cdce0cf217478ba93563
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