Chapter 4, "Performance," covered the basics of performance analysis and query tuning in PostgreSQL. As an administrator, you need to ensure that your users are getting the best possible performance from the database. Application developers are usually responsible for tuning the interaction between their application and the database, but the administrator is responsible for the performance of the database as a whole.
PostgreSQL provides a number of configuration parameters that control the query planner and optimizer. Starting with release 7.2, PostgreSQL also offers performance-monitoring tools that you can use to watch for poor performance before your users complain.
If you are an administrator, it's a good idea to review the material in Chapter 4. Understanding performance monitoring and tuning will help narrow your focus when you are tracking down a performance problem.
You should also formulate a plan for periodic routine maintenance. For example, you decide that you should VACUUM and VACUUM ANALYZE all tables every weekend. You may also want to CLUSTER important tables on a regular basis.