Modify Fields

In the previous sections, we learned that we could replace any document in a MongoDB collection once it has been inserted. During the replace operation, a document in the database will be replaced with a completely new document while keeping the same primary key. The replacement operations are quite useful when it comes to rectifying errors and to incorporating data changes or updates. However, in most cases, updates will affect only one or a few fields of a document. Think about any movie record from the sample_mflix dataset, where most of its fields (such as the title, cast, directors, duration, and so on) may never change. However, over a period of time, the movie may receive new comments, new reviews, and ratings.

The find and replace operation is very useful when all or most fields of a document are modified. But, using it to update only particular fields in the documents will not be easy. To do so, the replacement document you provide will need to have all the...