Extending SQL

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

• functions (starting in User-Defined Functions)
• aggregates (starting in User-Defined Aggregates)
• data types (starting in User-Defined Types)
• operators (starting in User-Defined Operators)
• operator classes for indexes (starting in Interfacing Extensions to Indexes)

• packages of related objects (starting in Packaging Related Objects into an Extension)

• How Extensibility Works

• The PostgreSQL Type System
• User-Defined Functions
• User-Defined Procedures
• Query Language (SQL) Functions
• Function Overloading
• Function Volatility Categories
• Procedural Language Functions
• Internal Functions
• C-Language Functions
• Function Optimization Information
• User-Defined Aggregates
• User-Defined Types
• User-Defined Operators
• Operator Optimization Information
• Interfacing Extensions to Indexes
• Packaging Related Objects into an Extension
• Extension Building Infrastructure