Deep dive into a SQL query

Have you ever wondered what actually happens inside PostgreSQL when you run a SQL query? Behind a simple SELECT statement lies a sophisticated pipeline involving parsing, semantic analysis, query rewriting, cost-based optimization, and a pull-based execution engine—built on decades of database research.

Deep Dive Into a SQL Query takes you on a complete journey through PostgreSQL's query processing internals. Starting from the moment a client establishes a connection, you'll follow a query through every stage of the pipeline: lexical analysis and parsing, semantic validation against the system catalog, rule-based rewriting, cost-based plan optimization, and iterator-based execution. Along the way, you'll explore how PostgreSQL manages memory, organizes data on disk, coordinates concurrent access, and returns results to the client.

This book is written for mid-level to senior software engineers who use databases every day but want to understand what happens beneath the SQL interface. Every technical detail is grounded in PostgreSQL's actual source code—not abstractions or hand-waving. By the end, you'll write better queries, diagnose performance problems with confidence, and understand why PostgreSQL behaves the way it does.