In addition to the system catalogs, PostgreSQL provides a number of built-in views. The system views provide convenient access to some commonly used queries on the system catalogs. Some of these views provide access to internal server state, as well.
Table 43-30 lists the system views described here. More detailed documentation of each view follows below. There are some additional views that provide access to the results of the statistics collector; they are described in Table 23-1.
The information schema (Chapter 32) provides an alternative set of views which overlap the functionality of the system views. Since the information schema is SQL-standard whereas the views described here are PostgreSQL-specific, it's usually better to use the information schema if it provides all the information you need.
Except where noted, all the views described here are read-only.