polyglot-sql

Core SQL parsing and dialect translation library for Rust. Parses, generates, transpiles, and formats SQL across 32 database dialects.

Part of the Polyglot project.

Features

• Parse SQL into a fully-typed AST with 200+ expression types
• Generate SQL from AST nodes for any target dialect
• Transpile between any pair of 32 dialects in one call
• Format / pretty-print SQL
• Fluent builder API for constructing queries programmatically
• AST traversal utilities (DFS/BFS iterators, transform, walk)
• Validation with syntax checking and error location reporting
• Schema module for column resolution and type annotation

Usage

Transpile

use polyglot_sql::{transpile, DialectType};

let result = transpile(
    "SELECT IFNULL(a, b) FROM t",
    DialectType::MySQL,
    DialectType::Postgres,
).unwrap();
assert_eq!(result[0], "SELECT COALESCE(a, b) FROM t");

You can also transpile through a Dialect handle directly — useful when you already hold one (e.g., for custom dialects) or need pretty-printed output:

use polyglot_sql::{Dialect, DialectType, TranspileOptions};

let mysql = Dialect::get(DialectType::MySQL);

// Built-in target via DialectType
let plain = mysql.transpile("SELECT IFNULL(a, b) FROM t", DialectType::Postgres).unwrap();

// Pretty-printed output via TranspileOptions
let pretty = mysql
    .transpile_with(
        "SELECT IFNULL(a, b) FROM t",
        DialectType::Postgres,
        TranspileOptions::pretty(),
    )
    .unwrap();

// Target a custom (or built-in) Dialect handle directly
let pg = Dialect::get(DialectType::Postgres);
let via_handle = mysql.transpile("SELECT IFNULL(a, b) FROM t", &pg).unwrap();

Parse + Generate

use polyglot_sql::{parse, generate, DialectType};

let ast = parse("SELECT 1 + 2", DialectType::Generic).unwrap();
let sql = generate(&ast[0], DialectType::Postgres).unwrap();
assert_eq!(sql, "SELECT 1 + 2");

Format With Guard Options

Formatting is protected by guard limits by default:

• max_input_bytes: 16 * 1024 * 1024
• max_tokens: 1_000_000
• max_ast_nodes: 1_000_000
• max_set_op_chain: 256

You can override these limits per call:

use polyglot_sql::{format_with_options, DialectType, FormatGuardOptions};

let options = FormatGuardOptions {
    max_input_bytes: Some(2 * 1024 * 1024),
    max_tokens: Some(250_000),
    max_ast_nodes: Some(250_000),
    max_set_op_chain: Some(128),
};

let formatted = format_with_options("SELECT a,b FROM t", DialectType::Postgres, &options).unwrap();
assert!(formatted[0].contains("SELECT"));

Guard failures include stable codes in the error message:

• E_GUARD_INPUT_TOO_LARGE
• E_GUARD_TOKEN_BUDGET_EXCEEDED
• E_GUARD_AST_BUDGET_EXCEEDED
• E_GUARD_SET_OP_CHAIN_EXCEEDED

Fluent Builder

use polyglot_sql::builder::*;

// SELECT id, name FROM users WHERE age > 18 ORDER BY name LIMIT 10
let expr = select(["id", "name"])
    .from("users")
    .where_(col("age").gt(lit(18)))
    .order_by(["name"])
    .limit(10)
    .build();

Expression Helpers

use polyglot_sql::builder::*;

// Column references (supports dotted names)
let c = col("users.id");

// Literals
let s = lit("hello");   // 'hello'
let n = lit(42);         // 42
let f = lit(3.14);       // 3.14
let b = lit(true);       // TRUE

// Operators
let cond = col("age").gte(lit(18)).and(col("status").eq(lit("active")));

// Functions
let f = func("COALESCE", [col("a"), col("b"), null()]);

CASE Expressions

use polyglot_sql::builder::*;

let expr = case()
    .when(col("x").gt(lit(0)), lit("positive"))
    .when(col("x").eq(lit(0)), lit("zero"))
    .else_(lit("negative"))
    .build();

Set Operations

use polyglot_sql::builder::*;

let expr = union_all(
    select(["id"]).from("a"),
    select(["id"]).from("b"),
)
.order_by(["id"])
.limit(5)
.build();

INSERT, UPDATE, DELETE

use polyglot_sql::builder::*;

// INSERT INTO users (id, name) VALUES (1, 'Alice')
let ins = insert_into("users")
    .columns(["id", "name"])
    .values([lit(1), lit("Alice")])
    .build();

// UPDATE users SET name = 'Bob' WHERE id = 1
let upd = update("users")
    .set("name", lit("Bob"))
    .where_(col("id").eq(lit(1)))
    .build();

// DELETE FROM users WHERE id = 1
let del = delete("users")
    .where_(col("id").eq(lit(1)))
    .build();

AST Traversal

use polyglot_sql::{parse, DialectType, traversal::*};

let ast = parse("SELECT a, b FROM t WHERE x > 1", DialectType::Generic).unwrap();
let columns = get_columns(&ast[0]);
let tables = get_tables(&ast[0]);

Validation

use polyglot_sql::{validate, DialectType};

let result = validate("SELECT * FORM users", DialectType::Generic);
// result contains error with line/column location

use polyglot_sql::{
    validate_with_schema, DialectType, SchemaColumn, SchemaTable, SchemaValidationOptions,
    ValidationSchema,
};

let schema = ValidationSchema {
    strict: Some(true),
    tables: vec![
        SchemaTable {
            name: "users".into(),
            schema: None,
            columns: vec![
                SchemaColumn {
                    name: "id".into(),
                    data_type: "integer".into(),
                    nullable: Some(false),
                    primary_key: true,
                    unique: false,
                    references: None,
                },
                SchemaColumn {
                    name: "email".into(),
                    data_type: "varchar".into(),
                    nullable: Some(false),
                    primary_key: false,
                    unique: true,
                    references: None,
                },
            ],
            aliases: vec![],
            primary_key: vec!["id".into()],
            unique_keys: vec![vec!["email".into()]],
            foreign_keys: vec![],
        },
    ],
};

let opts = SchemaValidationOptions {
    check_types: true,
    check_references: true,
    strict: None,
    semantic: true,
};

let result = validate_with_schema(
    "SELECT id FROM users WHERE email = 1",
    DialectType::Generic,
    &schema,
    &opts,
);
assert!(!result.valid);

Schema-aware validation emits stable codes such as:

• E200/E201 for unknown tables/columns
• E210-E217 and W210-W216 for type checks
• E220, E221, W220, W221, W222 for reference/FK checks

Tokenize

Access the raw token stream with full source position spans. Each token carries a Span with byte offsets and line/column numbers.

use polyglot_sql::{DialectType, Dialect};

let dialect = Dialect::new(DialectType::Generic);
let tokens = dialect.tokenize("SELECT a, b FROM t").unwrap();

for token in &tokens {
    println!("{:?} {:?} {:?}", token.token_type, token.text, token.span);
    // Select "SELECT" Span { start: 0, end: 6, line: 1, column: 1 }
    // Var    "a"      Span { start: 7, end: 8, line: 1, column: 8 }
    // ...
}

The Span struct provides:

Error Reporting

Parse and tokenize errors include source position information with line/column numbers and byte offset ranges, making it straightforward to provide precise error feedback.

use polyglot_sql::{parse, DialectType};

let result = parse("SELECT 1 +", DialectType::Generic);
if let Err(e) = result {
    println!("{}", e);            // "Parse error at line 1, column 11: ..."
    println!("{:?}", e.line());   // Some(1)
    println!("{:?}", e.column()); // Some(11)
    println!("{:?}", e.start());  // Some(10) — byte offset
    println!("{:?}", e.end());    // Some(11) — byte offset (exclusive)
}

The Error enum provides line(), column(), start(), and end() accessors that return Option<usize> for Parse, Tokenize, and Syntax error variants:

use polyglot_sql::error::Error;

let err = Error::parse("Unexpected token", 3, 15);
assert_eq!(err.line(), Some(3));
assert_eq!(err.column(), Some(15));

// Generation errors don't carry position info
let err = Error::generate("unsupported expression");
assert_eq!(err.line(), None);

Supported Dialects

Athena, BigQuery, ClickHouse, CockroachDB, Databricks, Doris, Dremio, Drill, Druid, DuckDB, Dune, Exasol, Fabric, Hive, Materialize, MySQL, Oracle, PostgreSQL, Presto, Redshift, RisingWave, SingleStore, Snowflake, Solr, Spark, SQLite, StarRocks, Tableau, Teradata, TiDB, Trino, TSQL

Feature Flags

License

MIT