The Query Parser and Planner
When you send SQL to a database, the text first passes through a parser and then a planner. These early stages turn human readable text into a precise internal form before any data is touched.
Parsing
The parser checks that the SQL is valid grammar and builds an abstract syntax tree, a tree that captures the structure of the statement. It catches typos and missing keywords here, long before execution.
Binding and planning
After parsing, the engine binds names. It looks up each table and column in the catalog, resolves types, and rejects references to things that do not exist. The planner then produces an initial query plan, a tree of operators such as scans and joins that describes how to compute the answer.
- The parser validates syntax and builds a tree.
- Binding resolves names against the catalog.
- The planner turns the bound tree into operators.
Key idea
Parsing and planning convert SQL text into a validated, name resolved operator tree that later stages can optimize and run.