36. Extending SQL

In the sections that follow, we will discuss how you can extend the PostgreSQL SQL query language by adding:

• functions (starting in Section 36.3)
• aggregates (starting in Section 36.12)
• data types (starting in Section 36.13)
• operators (starting in Section 36.14)
• operator classes for indexes (starting in Section 36.16)
• packages of related objects (starting in Section 36.17)