- Predicate pushdown now splits AND predicates and pushes each to
the correct side of the join (left table vs right table)
- FROM clause no longer duplicates tables that appear in JOINs
- Constant folding no longer mangles date literals (skips strings)
- Cost model: hash join uses build/probe costs, nested_loop uses
per-row probe cost instead of cartesian product
- Physical operator selection defaults to hash join for medium+ tables
- Two-pass SQL generation: collect join tables first, then emit FROM
- Demo shows 86% cost reduction on users/orders query, 25% on
departments/employees query from ekeric13/sql-query-optimization-guide
SQLOptimizer.speckdl: state machine spec for the optimizer pipeline
(Parsing → Rewriting → Planning → Generating → Done, plus Failed)
SQLOptimizer-runtime.ts: working TypeScript runtime that actually
optimizes SQL queries:
- Parses SELECT/FROM/JOIN/WHERE/GROUP BY/ORDER BY/LIMIT
- Builds plan trees with cardinality estimation
- Predicate pushdown (splits AND predicates per table)
- Constant folding (evaluates arithmetic in predicates)
- Column pruning
- Physical operator selection (hash/merge/nested_loop joins)
- Cost estimation per plan node
- SQL generation from optimized plan tree
Known issues:
- Predicate pushdown needs to split AND predicates per table
- FROM clause duplicate when both listed and joined
- Cost model needs tuning (hash join startup cost shouldn't exceed
nested loop savings for medium inputs)
Both files pass tsc --noEmit clean.
