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5 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 5.3 User-Defined Functions)
• aggregates (starting in section 5.10 User-Defined Aggregates)
• data types (starting in section 5.11 User-Defined Types)
• operators (starting in section 5.12 User-Defined Operators)
• operator classes for indexes (starting in section 5.14 Interfacing Extensions To Indexes)