squonk

An extensible, fast, multi-dialect SQL tokenizer and parser for Rust that hands back an owned, 'static syntax tree you can inspect, rewrite, and render back to SQL.

Quickstart

cargo add squonk

use squonk::parse;

// Parse: ANSI SQL becomes an owned, `'static` syntax tree.
let parsed = parse("select 1 +  2").expect("well-formed SQL parses");

// Inspect: statements come back in source order.
assert_eq!(parsed.statements().len(), 1);

// Render: canonical output normalizes keyword case and spacing.
assert_eq!(parsed.to_string(), "SELECT 1 + 2");

The tree is fully owned (it moves the source in, so it never borrows your input) and walks the whole statement: match a Statement to inspect it, edit it in place with the generated Visit / VisitMut walks, or render it back out — canonical, fully parenthesized, or PII-redacted. The crate docs carry worked parse, inspect, render, rewrite, transpile, and error-recovery examples.

Dialects

Several dialects ship (BuiltinDialect::ALL is the selectable list). Ansi — the SQL-standard baseline that parse defaults to — is always compiled; every other dialect is an opt-in cargo feature, so a default build stays lean:

[dependencies]
squonk = { version = "2.0", features = ["postgres"] }

postgres, mysql, sqlite, duckdb, the permissive lenient "parse-anything" union, and the conservative bigquery, clickhouse, databricks, hive, mssql, redshift, and snowflake presets each gate one dialect; full turns on all of them. Select a statically typed dialect with parse_with and ParseConfig, or choose a compiled preset at runtime with parse_builtin; render for a target dialect with the Renderer, or transpile between two in one call. Each engine-backed dialect is held to its real engine by a differential accept/reject oracle, so its surface is engine-verified rather than merely self-consistent; the conservative presets are ANSI-derived and ship without an oracle (excluded from the oracle conformance sets, they reject unmodelled syntax cleanly). The per-dialect 100%-conformance programmes are ongoing, so this is verified breadth, not a finished spec-level audit.

Status

Stable (2.0) — the public API is frozen and covered by the SemVer contract in docs/stable-api.md; no breaking change lands without a major bump. The engine-backed dialects (ANSI, PostgreSQL, MySQL, SQLite, DuckDB) are the strongest surface, each held to its real engine by a differential oracle; the conservative presets reject unmodelled syntax cleanly. The per-dialect conformance work continues additively under 2.x, with design rationale recorded in docs/adr/.

On the repository's frozen 256-statement publication workload, the Rust API measured 2.37× the full-AST throughput of datafusion-sqlparser-rs on the recorded Linux host. The exact work unit, versions, retained-memory results, uncertainty, and limitations are documented in the performance report.

Documentation

API reference and worked examples: docs.rs/squonk
Internals and architecture: the workspace README

The AST itself lives in the near-dependency-free squonk-ast crate (its only non-optional dependency is the thin-vec micro-leaf; serde is opt-in) and is re-exported here as squonk::ast, so most users only need this crate.

License