Building on cost estimation, this chapter covers how the planner generates and evaluates different execution paths. We will dissect the algorithms behind sequential scans vs. index scans, and analyze join strategies (Nested Loop, Hash Join, Merge Join). The chapter concludes with a look at Genetic Query Optimization (GEQO) for handling complex queries with many joins.

Outside Reading

• Official Docs: Chapter 61: Genetic Query Optimizer. (Explains the traveling salesperson problem as it applies to join order).
• Whitepaper: The System R Relational Database Management System (Astrahan et al., 1976). Assign the section on dynamic programming for join optimization, as Postgres still relies on this foundational math.
• GitHub Source: src/backend/optimizer/geqo/geqo_main.c. Review the genetic algorithm heuristics.