{"id":48431,"date":"2019-02-01T12:39:52","date_gmt":"2019-02-01T07:09:52","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=48431"},"modified":"2021-05-09T13:07:21","modified_gmt":"2021-05-09T07:37:21","slug":"mongodb-objectid-and-atomic-operations","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/mongodb-objectid-and-atomic-operations\/","title":{"rendered":"MongoDB Objectid | MongoDB Atomic Operations (Models & Commands)"},"content":{"rendered":"

In the last tutorial we had learned, covered queries and analyzing queries<\/strong>. Now we will discuss MongoDB ObjectId with driver ObjectId constructor and static methods. Along with this, we will study about MongoDB Atomic Operations with model and commands.<\/p>\n

What is MongoDB ObjectId?<\/h2>\n

ObjectId is the default primary key for a MongoDB document<\/strong> and is usually found in the _id field in an inserted document. Let\u2019s take an example to understand this.<\/p>\n

{\r\n\"_id\": ObjectId(\"54759eb3c090d83494e2d804\")\r\n}<\/pre>\n
It is a 12-byte binary BSON type that contains any 12 bytes. To generate MongoDB ObjectId, we will be using a default algorithm. An ObjectId\u2019s 12 bytes will then contain the following:<\/p>\n\n\n\n<\/colgroup>\n\n\n\n\n\n\n
Size<\/strong><\/td>\nDescription<\/strong><\/td>\n<\/tr>\n
4 bytes<\/td>\n\n
\n
A 4-byte value representing the seconds
\nsince the Unix epoch<\/div>\n<\/div>\n<\/td>\n<\/tr>\n
3 bytes<\/td>\n3-byte machine identifier<\/td>\n<\/tr>\n
2 bytes<\/td>\n2-byte process id<\/td>\n<\/tr>\n
3 bytes<\/td>\n\n
\n
3-byte counter, starting with a random value<\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
Let\u2019s take an example to understand this better.<\/p>\n
var ObjectId = require('mongodb').ObjectID\r\n\r\nvar id = new ObjectId();\r\nconsole.log(id)<\/pre>\n
It will print a hexadecimal representation of the 12 byte ObjectId the driver generated.<\/p>\n
Here, we will create the definition of a 12 byte ObjectId.<\/p>\n
var ObjectId = require('mongodb').ObjectID\r\n\r\nvar id = new ObjectId(\"aaaaaaaaaaaa\");\r\nconsole.log(id)<\/pre>\n
It will print the hexadecimal value 616161616161616161616161, which corresponds to the given string.<\/p>\n
Driver ObjectId Constructor Methods<\/h2>\n
The driver allows you to create MongoDB ObjectId in many different kinds of ways. You can pass a 12-byte string or a 24-byte hexadecimal representation and arguments as well.<\/p>\n
var ObjectId = require('mongodb').ObjectID\r\nvar id = new ObjectId();<\/pre>\n
Now, it creates a new generated ObjectId using the algorithm outlined above.<\/p>\n
var ObjectId = require('mongodb').ObjectID\r\nvar id = new ObjectId(\"aaaaaaaaaaaa\");<\/pre>\n
Now, creates a new specific MongoDB ObjectId12-byte12 byte string.<\/p>\n
var ObjectId = require('mongodb').ObjectID\r\nvar id = new ObjectId(\"616161616161616161616161\");<\/pre>\n
It is useful for passing back Id\u2019s from a web application.<\/p>\n
Driver ObjectId Static Methods<\/h2>\n
This is meant to be helpful in making it more explicit what your intention is when creating a new ObjectId in MongoDB.<\/p>\n
var ObjectId = require('mongodb').ObjectID\r\nvar id = ObjectId.createPk();<\/pre>\n
Now, we will create a new instance.<\/p>\n
var ObjectId = require('mongodb').ObjectID\r\nvar id = ObjectId.createFromTime(5000);<\/pre>\n
Now, creating an ObjectId from a second timestamp.<\/p>\n
var ObjectId = require('mongodb').ObjectID\r\nvar id = ObjectId.createFromHexString(\"616161616161616161616161\");\r\nDriver ObjectId Instance methods<\/pre>\n
Some static methods on a MongoDB ObjectId instance are the following:<\/p>\n