To get index lists

db.tableName.getIndexes()

To set Index

db.contact.createIndex({age:1})

It will create index in asc order

db.contact.createIndex({age:-1})

It will create index in desc order

db.contact.createIndex({age:1, gender:1})

Create group of index with age and gender both done in asc order.

To Delete Index

db.contact.dropIndex({"age": 1})

Value of key need to be 1 or -1 based on how index was created. If asc, 1 and for desc it is -1

Create Unique index

db.contact.createIndex({email:1},{unique: true})

Create Unique Index on email field. While inserting data one have to provide email field, else it would throw error

db.users.createIndex({email: 1}, {unique: true, partialFilterExpression: {email: {$exists: true}}})

Only create index for email field if exists. If field doesn’t exists, no issue even while inserting new data.

TTL Index

db.sessions.createIndex({createdAt: 1}, {expireAfterSeconds: 10})

create index for CreatedAt (the column should be datetime type) and destroy the record having that index after 10 seconds.