MongoDB Auto Increment ID

In this MongoDB tutorial, we are going to learn how to generate the MongoDB Auto Increment ID.

We want the _id field in an auto-increment sequence starting from 1,2,3 up to n. So consider the following documents.

{
   "_id":1,
   "item_name": "The Higgler",
   "specification": "Book",
   "series": "Romance"
}

MongoDB doesn’t support auto-increment features, unlike a relational database. We can perform this functionality by creating a collection and the collection will have a document that tracks the unique identifier.

Let’s follow the below steps to generate the MongoDB auto-increment id:

1. Generate a collection
2. Insert a document into a collection
3. Insert the record into a collection
4. Database sequence
5. Create a JavaScript function
6. Use JavaScript function
7. View inserted a record from store collection

1. Generate a collection:

We create a collection with any name (example) by using the createCollection() method.

> db.createCollection("example")
{ "ok" : 1 }

2. Insert a document into a collection:

Insert a document into the student collection which is having item_id its key.

{
   "_id" : "item_id",
   "sequence_value": 0
}

Here, The sequence_value field is used to keeps track of the last value of the sequence.

3. Insert the record into a collection:

We will insert the above record into the example collection by using the insert() method.

> db.example.insert( {_id: "item_id" , sequence_value : 0 } )
WriteResult({ "nInserted" : 1 })

4. Database sequences:

Use this student collection as a database sequence to auto-generate the item_id:

> db.student.insert( {_id: "item_id" , sequence_value : 0 } )

Read MongoDB get collection size

5. Create a JavaScript Function:

Now, we will create a getNextSequence JavaScript function to increment the value of the sequence_value by 1 and also return the updated sequence number.

> function getNextSequence(sequenceName){
    var sequenceDocument = db.example.findAndModify({
       query:{_id: sequenceName },
       update: {$inc:{sequence_value:1}},
       new:true
    });
    return sequenceDocument.sequence_value;
}

6. Use JavaScript Function:

Now we will use the above JavaScript getNextSequence function to create an auto-increment sequence new document and assign the returned sequence value as the item_id field.

Here, we are inserting the following two documents into the example collection:

db.example.insert({
    "_id": getNextSequence("item_id"),
    "item_name": "The Grass is Always Greener",
    "specification": "book",
    "series": "Modern Times",
})

db.example.insert({
    "_id": getNextSequence("item_id"),
    "item_name": "Murder!",
    "specification": "book",
    "series": "Crime",
})

Here, we have used the getNextSequence function to set value for the _id field.

7. View inserted a record from the stored collection:

We will check the documents of the example collection by using the find() method.

> db.example.find().pretty()

Now, the query will return the document having the auto-increment id field.

Thus, By following all the steps, we successfully create a MongoDB auto-increment id.

You may also like to read the following MongoDB tutorials.

• MongoDB two-phase commit
• MongoDB find string contains
• MongoDB find by ID
• MongoDB text search partial words
• Create index in MongoDB
• MongoDB Update Documents
• Export MongoDB to CSV
• MongoDB remove a field from the document
• MongoDB join two collections
• Import CSV into MongoDB
• MongoDB drop collection

So in this tutorial, we have learned about “MongoDB Auto Increment ID” and covered it with the help of an example.