Anatomy of a SQL Engine
a year ago
- #Query Optimization
- #SQL
- #Database
- SQL engines perform parsing, binding, plan simplification, join exploration, plan costing, execution, and spooling results.
- Parsing converts a query into an abstract syntax tree (AST) using left-recursive Yacc grammar for efficiency.
- Binding matches AST identifiers to database catalog symbols, similar to variable scoping in programming languages.
- Plan simplification regularizes SQL syntax into a canonical form for better execution performance.
- Join exploration involves searching for optimal join configurations and costing them based on database statistics.
- Execution converts the final plan into an executable format, often using row-based iterators.
- Spooling translates result rows into the appropriate format for network transmission.
- Future improvements may include unifying intermediate representations and optimizing memory management.