In this recipe, we will look at creating unique indexes on a collection. Unique indexes, from the name itself, tell us that the value with which the index is created has to be unique. What if the collection already has data and we want to create a unique index on a field whose value is not unique in the existing data?
Obviously, we cannot create the index, and it will fail. There is, however, a way to drop the duplicates and create the index. Curious how this can be achieved? Yes? Keep reading this recipe.
For this recipe, we will create a collection called userDetails. We will need the server to be up and running. Refer to the Single node installation of MongoDB recipe in Chapter 1, Installing and Starting the MongoDB Server, to learn how to start the server. Also, start the shell with the UniqueIndexData.js script loaded. This script will be available on the book's website for download...