• MongoDB is one of the leading NoSQL database. It is written in C++ Program.
• It provides high performance and availability and high scalable.
• Indexing in MongoDB is used to make query processing more efficient.
• The MongoDB scan every document in the collection and retrieve only those documents that match the query, where there is no indexing.
• Indexes are special data structures that stores some information related to the documents such that it becomes easy for MongoDB to find the right data file.
• Indexes are ordered by the value of the field specified in the index.

Index Creating :

•  createIndex() is a method that allows user to create an index.

Syntax :

For Example,

db.mycol.createIndex({“age”:1})
{
“createdCollectionAutomatically” : false,
“numIndexesBefore” : 1,
“numIndexesAfter” : 2,
“ok” : 1
} 

• In createIndex() method, there are five types of parameters:

1. 1. background (Boolean)
   2. unique (Boolean)
   3. name (string)
   4. sparse (Boolean)

Index for Drop :

• dropIndex() is a method that allows users to drop an index.
• This method can delete only one index at a time.
• MongoDB provides the dropIndexes() method that takes multiple indexes as its parameters.

Syntax :

Get description of all indexes :

• It will retrieve all the description of the indexes created within the collection.

Syntax :