Organizing Related Data - Learning Apache Cassandra - page 72

Summary
In this chapter, we were introduced to the concept of compound primary keys, and learned
that a primary key consists of one or more partition keys and, optionally, one or more clus-
tering columns. We saw how partition keys—the only type of key we had previously en-
countered—can group related rows together, and how clustering columns provide an order
for these rows within each partition.
Compound primary keys allow us to build a table containing users' status updates because
they expose two important structures: grouping of related rows, and ordering of rows. In
the user_status_updates table, we encoded the relationship between users and their
status updates implicitly in the structure of the primary key; the partition key refers to the
parent row in the users table. We also explored the use of static columns to make this re-
lationship explicit, storing all the information about users and their status updates in a
single table.
In Chapter 4 , Beyond Key-Value Lookup , we will dive into new ways of interacting with
data that is organized using compound primary keys, allowing us to build functionality in
our application for viewing users' timelines in a variety of interesting ways.