PostgreSQL's extensibility is well known. Most people have heard of user types, user operators, the new extension capability, and such. But few know about hooks in PostgreSQL. This talk will cover all kinds of hooks available in PostgreSQL, and will show some tools using them already. Since the 8.3 release, the PostgreSQL developers add many hooks in PostgreSQL. Some extensions already make use of such hooks in the planner and in the executor. pgstatstatements is one of the various examples available. This talk will give a large overview of the hook system, and how to use it. We'll also see some of the extensions making use of them.