pg_query.rs  

This Rust library uses the actual PostgreSQL server source to parse SQL queries and return the internal PostgreSQL parse tree.

It also allows you to normalize queries (replacing constant values with $1, etc.) and parse these normalized queries into a parse tree again.

When you build this library, it builds parts of the PostgreSQL server source (see libpg_query), and then statically links it into this library.

You can find further examples and a longer rationale for the original Ruby implementation here. The Rust version tries to have a very similar API.

Examples

Parsing a query

use pg_query::NodeRef;

let result = pg_query::parse("SELECT * FROM contacts", 0);
assert!(result.is_ok());
let result = result.unwrap();
assert_eq!(result.tables(), vec!["contacts"]);
assert!(matches!(result.protobuf.nodes()[0].0, NodeRef::SelectStmt(_)));

Normalizing a query

let result = pg_query::normalize("SELECT 1 FROM x WHERE y = (SELECT 123 FROM a WHERE z = 'bla')").unwrap();
assert_eq!(result, "SELECT $1 FROM x WHERE y = (SELECT $2 FROM a WHERE z = $3)");

Fingerprinting a query

let result = pg_query::fingerprint("SELECT * FROM contacts.person WHERE id IN (1, 2, 3, 4);", 0, 0).unwrap();
assert_eq!(result.hex, "5735f5c64dd9f68e");

Fingerprinting allows you to identify similar queries that are different only because of the specific object being queried (e.g. different object ids in the WHERE clause) or because of formatting. It is intended to be a superset of the Postgres queryid mechanism: constant values are ignored, so ... WHERE id = 123 and ... WHERE id = 456 get the same fingerprint.

Postgres 18 significantly changed how schema names and table aliases in FROM clauses are handled for queryid, and libpg_query follows that by default:

• Postgres 17 and earlier: the schema name was significant, and table aliases were always ignored.
• Postgres 18 (default): schema names are ignored, and a table alias (if present) is used instead of the relation name.

// Postgres 18 behaviour (default): schema is ignored and the alias replaces the relation name
let a = pg_query::fingerprint("SELECT * FROM public.users u", 0, 0).unwrap();
let b = pg_query::fingerprint("SELECT * FROM myschema.users u", 0, 0).unwrap();
assert_eq!(a.hex, b.hex);

// Postgres 17 compatible fingerprints take the schema into account
let a = pg_query::fingerprint("SELECT * FROM public.users u", 0, pg_query::FingerprintOptions::RANGEVAR_PG17_COMPAT).unwrap();
let b = pg_query::fingerprint("SELECT * FROM myschema.users u", 0, pg_query::FingerprintOptions::RANGEVAR_PG17_COMPAT).unwrap();
assert_ne!(a.hex, b.hex);

Available fingerprint options (combinable, passed as the third fingerprint argument to pg_query::fingerprint):

See https://github.com/pganalyze/libpg_query/wiki/Fingerprinting for the full fingerprinting rules.

Scanning a query's tokens without protobuf

let tokens = pg_query::scan_tokens("SELECT 1").unwrap();
assert_eq!(tokens.len(), 2);
assert_eq!(tokens[0].start, 0);
assert_eq!(tokens[0].end, 6);

Detecting utility statements

let result = pg_query::is_utility_stmt("SELECT 1; SHOW fsync;").unwrap();
assert_eq!(result, vec![false, true]);

Deparsing a query

use pg_query::DeparseOptions;

let parsed = pg_query::parse("SELECT 1 -- comment\n", 0).unwrap();
let output = pg_query::deparse(&parsed.protobuf, DeparseOptions::default()).unwrap();
assert_eq!(output, "SELECT 1");

// With comments extracted and re-inserted, pretty-printed:
let comments = pg_query::deparse_comments_for_query("SELECT 1 -- comment\n").unwrap();
let output = pg_query::deparse(
    &parsed.protobuf,
    DeparseOptions {
        comments,
        pretty_print: true,
        ..Default::default()
    },
)
.unwrap();
assert!(output.contains("-- comment"));

Truncating a query

let query = "INSERT INTO \"x\" (a, b, c, d, e, f) VALUES ($1)";
let result = pg_query::parse(query, 0).unwrap();
assert_eq!(result.truncate(32).unwrap(), "INSERT INTO x (...) VALUES (...)");

Credits

Thanks to Paul Mason for his work on pg_parse that this crate is based on.

After version 0.6.0, Paul donated the pg_query crate to the pganalyze team. pg_parse is a lighter alternative that focuses on query parsing, while pg_query aims for feature parity with the Ruby gem.

License

PostgreSQL server source code, used under the PostgreSQL license. Portions Copyright (c) 1996-2023, The PostgreSQL Global Development Group Portions Copyright (c) 1994, The Regents of the University of California

All other parts are licensed under the MIT license, see LICENSE file for details. Copyright (c) 2021 Paul Mason paul@form1.co.nz Copyright (c) 2021-2023, Duboce Labs, Inc. (pganalyze) team@pganalyze.com