PostgreSQL's query optimizer is a critical component that determines the efficiency of query execution. This article offers a comprehensive source code walkthrough of the standard_planner() function in PostgreSQL 18.3, detailing the step-by-step process from receiving a Query structure to producing a PlannedStmt. Key topics include the planner's initialization, subquery handling, join planning, and path generation. The analysis is based on the actual codebase and provides insights into the optimizer's design decisions, such as how it handles different query types and optimization levels. For database engineers and contributors, understanding this flow is essential for debugging performance issues or contributing patches. The article avoids generic explanations and focuses on the concrete implementation, making it a valuable reference for those working with PostgreSQL internals.
This article provides a detailed source-level walkthrough of PostgreSQL 18.3's standard_planner() function, explaining how the query optimizer transforms a Query into a PlannedStmt. It is valuable for developers working on database internals or performance tuning.