The course concludes by exploring PostgreSQL's extensibility. Students will learn the architecture behind creating custom data types, writing background workers in C, and leveraging extension hooks to modify the parser, planner, or executor behavior without altering the core source code.

Outside Reading

• Official Docs: Chapter 38: Extending SQL and Chapter 40: C-Language Functions.
• Official Docs: Chapter 48: Background Worker Processes.
• GitHub Source: src/include/optimizer/planner.h. Have students locate the planner_hook variable to see exactly how C-extensions intercept the core query planner.