1. Database Cluster, Databases and Tables

This chapter provides an overview of PostgreSQL’s primary storage entities: database clusters, databases, and tables.

A database cluster is the entire set of databases managed by a PostgreSQL instance, and a database is a logical collection of tables. Tables are the basic structures that store user data.

These entities form the foundation of PostgreSQL’s data management. PostgreSQL provides various features to store, access, modify, and protect data organized within these structures.

This hierarchy is essential to understanding how PostgreSQL manages data internally. Later chapters examine the processes, memory structures, storage structures, and other mechanisms that support these entities.

Together with the next chapter, this chapter provides the background required to understand the advanced topics in subsequent chapters.