Cursor Methods - MongoDB Shell

In MongoDB Shell, cursor methods provide a way to iterate over the documents in a collection. In this page, we will discuss the most common cursor methods and how to use them.

Syntax

The syntax for cursor methods in MongoDB Shell is as follows:

cursor.<method>()

Here, cursor represents the cursor object, and <method> represents the cursor method.

Example

Let's start with an example collection named "students" that contains the following documents:

{
    "_id": 1,
    "name": "John",
    "age": 25
}
{
    "_id": 2,
    "name": "Sarah",
    "age": 22
}
{
    "_id": 3,
    "name": "Mike",
    "age": 28
}

To retrieve all the documents in the "students" collection, we can use the find() method:

var cursor = db.students.find();

This creates a cursor object that we can use to iterate over the documents in the collection.

Output

The find() method returns a cursor object that can be printed to the console. When we execute the above command in the MongoDB Shell, it returns the following output:

{ "_id" : 1, "name" : "John", "age" : 25 }
{ "_id" : 2, "name" : "Sarah", "age" : 22 }
{ "_id" : 3, "name" : "Mike", "age" : 28 }

Explanation

Cursor methods in MongoDB Shell provide a way to iterate over the documents in a collection. These methods provide several ways to manipulate and filter the data on the fly, without needing to load the entire collection into memory.

Some common cursor methods include:

• forEach() : Iterates over the documents in the cursor and applies a function to each document.
• sort() : Sorts the documents in the cursor based on a specified field.
• limit() : Limits the number of documents returned by the cursor.
• skip() : Skips a specified number of documents from the beginning of the cursor.
• count() : Returns the number of documents in the cursor.
• toArray() : Converts the cursor to an array.

Use

Cursor methods in MongoDB Shell are used in conjunction with the find() method to iterate over the documents in a collection and apply various manipulations on them.

These methods can be used to retrieve a subset of the data, filter the results, sort the data, and perform other manipulations on the data.

Important Points

• Cursor methods provide a way to iterate over the documents in a collection and apply various manipulations on them.
• Cursor methods can be used to retrieve a subset of the data, filter the results, sort the data, and perform other manipulations on the data.

Summary

In this page, we discussed cursor methods in MongoDB Shell and how to use them to manipulate the data in a collection. We covered the syntax, example, output, explanation, use, and important points of cursor methods. By using cursor methods, you can effectively manipulate the data in your MongoDB collections and perform other complex operations on it.