PostgreSQL, Second Edition

How PostgreSQL Organizes Data

Before you can really dig into the details of performance tuning, you need to understand some of the basic architecture of PostgreSQL.

You already know that in PostgreSQL, data is stored in tables and tables are grouped into databases. At the highest level of organization, databases are grouped into clusters—a cluster of databases is serviced by a postmaster.

Let's see how this data hierarchy is stored on disk. You can see all databases in a cluster using the following query:

perf=# SELECT datname, oid FROM pg_database;
  datname  |  oid
-----------+-------
 perf      | 16556
 template1 |     1
 template0 | 16555

From this list, you can see that I have three databases in this cluster. You can find the storage for these databases ...