Easy Tutorial
Mongodb Mongostat Mongotop Mongodb Regular Expression Mongodb Aggregate Mongodb Remove Mongodb Dropdatabase Mongodb Database References Mongodb Limit Skip Mongodb Php Mongodb Indexing Limitations Working With Rockmongo Mongodb Sharding Mongodb Covered Queries Mongodb Install Php Driver Mongodb Update Mongodb Capped Collections Mongodb Databases Documents Collections Mongodb Atomic Operations Mongodb Replication Mongodb Analyzing Queries Mongodb Advanced Indexing Mongodb Linux Install Mongodb Autoincrement Sequence Mongodb Map Reduce Mongodb Relationships Mongodb Create Collection Mongodb Text Search Mongodb Objectid Mongodb Osx Install Mongodb Gridfs Mongodb Window Install Mongodb Operators Php7 Mongdb Tutorial Mongodb Intro Mongodb Mongodump Mongorestore Mongodb Tutorial Mongodb Insert Mongodb Sort Mongodb Delete Collection Mongodb Java Mongodb Query Mongodb Operators Type Mongodb Connections Mongodb Indexing Nosql Mongodb Create Database
❮ Mongodb Text Search Mongodb Osx Install ❯

MongoDB ObjectId

In the previous chapters, we have already used MongoDB's ObjectId.

In this chapter, we will understand the structure of ObjectId.

ObjectId is a 12-byte BSON type data with the following format:

Every document stored in MongoDB must have an "_id" key. The value of this key can be of any type, with ObjectId being the default.

Within a collection, each document has a unique "_id" value to ensure that each document in the collection can be uniquely identified.

The main reason MongoDB uses ObjectId instead of other conventional methods (like auto-incremented primary keys) is that synchronizing auto-incremented primary key values across multiple servers is both laborious and time-consuming.

Creating a New ObjectId

Use the following code to generate a new ObjectId:

>newObjectId = ObjectId()

The above statement returns the following uniquely generated id:

ObjectId("5349b4ddd2781d08c09890f3")

You can also use a generated id to replace the ObjectId automatically generated by MongoDB:

>myObjectId = ObjectId("5349b4ddd2781d08c09890f4")

Timestamp of Document Creation

Since the ObjectId stores a 4-byte timestamp, you do not need to save a timestamp field for your document. You can obtain the creation time of the document using the getTimestamp function:

>ObjectId("5349b4ddd2781d08c09890f4").getTimestamp()

The above code will return the creation time of the document in ISO format:

ISODate("2014-04-12T21:49:17Z")

Converting ObjectId to String

In some cases, you may need to convert the ObjectId to a string format. You can use the following code:

>new ObjectId().str

The above code will return the string in GUID format:

5349b4ddd2781d08c09890f3
❮ Mongodb Text Search Mongodb Osx Install ❯