pgsql-parser/README.md

The real PostgreSQL query parser

# pgsql-parser 

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The real PostgreSQL parser for Node.js. Built with the actual [PostgreSQL parser](https://github.com/pganalyze/libpg_query), `pgsql-parser` delivers true-to-spec SQL parsing and reconstruction. Transform SQL queries into ASTs, modify them programmatically, and convert them back to SQL with complete fidelity.

## Installation

```sh
npm install pgsql-parser
```

## Features

* 🔄 **Symmetric Parsing & Deparsing** – Parse SQL to AST and reconstruct it back to SQL with perfect round-trip accuracy
* 🧪 **Battle-Tested Reliability** – Validated against 23,000+ SQL statements ensuring production-grade stability  
* 🔧 **Direct from PostgreSQL** – Uses the official Postgres C parser compiled to WebAssembly for 100% spec compliance
* 🚀 **WebAssembly Powered:** - Cross-platform compatibility without native dependencies.
* 🛠️ **AST Manipulation:** - Easily modify parts of a SQL statement through the AST.

## API

The package exports both async and sync methods. Async methods handle initialization automatically, while sync methods require explicit initialization.

⚠️ If you don't need the parser functionality, consider using the TS-only (no WASM, zero runtime dependencies) [`pgsql-deparser`](https://github.com/constructive-io/pgsql-parser/tree/main/packages/deparser) for a super fast, lightweight deparser. Battle-tested with 23,000+ SQL statements 🚀

### Async Methods (Recommended)

```typescript
import { parse, deparse } from 'pgsql-parser';

// Parse SQL to AST
const stmts = await parse('SELECT * FROM test_table');

// Deparse AST back to SQL
const sql = await deparse(stmts);
```

### Sync Methods

Sync methods require explicit initialization using `loadModule()`:

```typescript
import { loadModule, parseSync, deparseSync } from 'pgsql-parser';

// Initialize first (required for sync methods)
await loadModule();

// Now safe to use sync methods
const stmts = parseSync('SELECT * FROM test_table');
const sql = deparseSync(stmts);
```

**Note:** We recommend using async methods as they handle initialization automatically. Use sync methods only when necessary, and always call `loadModule()` first.

## Parser Example

Rewrite part of a SQL query:

```js
import { parse, deparse } from 'pgsql-parser';

const stmts = await parse('SELECT * FROM test_table');

// Assuming the structure of stmts is known and matches the expected type
stmts[0].RawStmt.stmt.SelectStmt.fromClause[0].RangeVar.relname = 'another_table';

console.log(await deparse(stmts));

// SELECT * FROM "another_table"
```

## Deparser Example

The `pgsql-deparser` module serializes ASTs to SQL in pure TypeScript, avoiding the full parser's native dependencies. It's useful when only SQL string conversion from ASTs is needed, and is written in pure TypeScript for easy cross-environment deployment.

Here's how you can use the deparser in your TypeScript code, using [`@pgsql/utils`](https://github.com/constructive-io/pgsql-parser/tree/main/packages/utils) to create an AST for `deparse`:

```ts
import * as t from '@pgsql/utils';
import { RangeVar, SelectStmt } from '@pgsql/types';
import { deparse } from 'pgsql-deparser';

// This could have been obtained from any JSON or AST, not necessarily @pgsql/utils
const stmt: { SelectStmt: SelectStmt } = t.nodes.selectStmt({
  targetList: [
    t.nodes.resTarget({
      val: t.nodes.columnRef({
        fields: [t.nodes.aStar()]
      })
    })
  ],
  fromClause: [
    t.nodes.rangeVar({
      relname: 'some_table',
      inh: true,
      relpersistence: 'p'
    })
  ],
  limitOption: 'LIMIT_OPTION_DEFAULT',
  op: 'SETOP_NONE'
});

// Modify the AST if needed  
(stmt.SelectStmt.fromClause[0] as {RangeVar: RangeVar}).RangeVar.relname = 'another_table';

// Deparse the modified AST back to a SQL string
console.log(await deparse(stmt));

// Output: SELECT * FROM another_table
```

## Credits

Built on the excellent work of several contributors:

* **[Dan Lynch](https://github.com/pyramation)** — official maintainer since 2018 and architect of the current implementation
* **[Lukas Fittl](https://github.com/lfittl)** for [libpg_query](https://github.com/pganalyze/libpg_query) — the core PostgreSQL parser that powers this project
* **[Greg Richardson](https://github.com/gregnr)** for AST guidance and pushing the transition to WASM and multiple PG runtimes for better interoperability
* **[Ethan Resnick](https://github.com/ethanresnick)** for the original Node.js N-API bindings
* **[Zac McCormick](https://github.com/zhm)** for the foundational [node-pg-query-native](https://github.com/zhm/node-pg-query-native) parser

---

**🛠 Built by the [Constructive](https://constructive.io) team — creators of modular Postgres tooling for secure, composable backends. If you like our work, contribute on [GitHub](https://github.com/constructive-io).**

## Related

* [pgsql-parser](https://www.npmjs.com/package/pgsql-parser): The real PostgreSQL parser for Node.js, providing symmetric parsing and deparsing of SQL statements with actual PostgreSQL parser integration.
* [pgsql-deparser](https://www.npmjs.com/package/pgsql-deparser): A streamlined tool designed for converting PostgreSQL ASTs back into SQL queries, focusing solely on deparser functionality to complement `pgsql-parser`.
* [@pgsql/parser](https://www.npmjs.com/package/@pgsql/parser): Multi-version PostgreSQL parser with dynamic version selection at runtime, supporting PostgreSQL 15, 16, and 17 in a single package.
* [@pgsql/types](https://www.npmjs.com/package/@pgsql/types): Offers TypeScript type definitions for PostgreSQL AST nodes, facilitating type-safe construction, analysis, and manipulation of ASTs.
* [@pgsql/enums](https://www.npmjs.com/package/@pgsql/enums): Provides TypeScript enum definitions for PostgreSQL constants, enabling type-safe usage of PostgreSQL enums and constants in your applications.
* [@pgsql/utils](https://www.npmjs.com/package/@pgsql/utils): A comprehensive utility library for PostgreSQL, offering type-safe AST node creation and enum value conversions, simplifying the construction and manipulation of PostgreSQL ASTs.
* [@pgsql/traverse](https://www.npmjs.com/package/@pgsql/traverse): PostgreSQL AST traversal utilities for pgsql-parser, providing a visitor pattern for traversing PostgreSQL Abstract Syntax Tree nodes, similar to Babel's traverse functionality but specifically designed for PostgreSQL AST structures.
* [pg-proto-parser](https://www.npmjs.com/package/pg-proto-parser): A TypeScript tool that parses PostgreSQL Protocol Buffers definitions to generate TypeScript interfaces, utility functions, and JSON mappings for enums.
* [libpg-query](https://github.com/constructive-io/libpg-query-node): The real PostgreSQL parser exposed for Node.js, used primarily in `pgsql-parser` for parsing and deparsing SQL queries.

## Disclaimer

AS DESCRIBED IN THE LICENSES, THE SOFTWARE IS PROVIDED "AS IS", AT YOUR OWN RISK, AND WITHOUT WARRANTIES OF ANY KIND.

No developer or entity involved in creating Software will be liable for any claims or damages whatsoever associated with your use, inability to use, or your interaction with other users of the Software code or Software CLI, including any direct, indirect, incidental, special, exemplary, punitive or consequential damages, or loss of profits, cryptocurrencies, tokens, or anything else of value.