In the previous chapter, we created a structure that allows a user to follow other users. The goal of the follow system was to allow users to see all of their followed users' status updates in one place, which we'll call the home timeline. In this chapter, we will build a table to store users' home timelines.
The follow structures in Chapter 5, Establishing Relationships, introduced the concept of denormalization, the practice of storing the same piece of data in more than one place in order to optimize read performance. The denormalization we used for follows was fairly mild; however, each follow relationship is stored in exactly two places. For home timelines, we will create a much more aggressively denormalized data structure: a given piece of data will be stored in an arbitrary number of places.
While this highly denormalized structure will be the end result of our work in this chapter, we'll explore several approaches along the way...