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https://github.com/sqlparser-rs/sqlparser-rs

Extensible SQL Lexer and Parser for Rust
https://github.com/sqlparser-rs/sqlparser-rs

parser rust sql

Last synced: 13 days ago
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Extensible SQL Lexer and Parser for Rust

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# Extensible SQL Lexer and Parser for Rust



[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)

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This crate contains a lexer and parser for SQL that conforms with the

[ANSI/ISO SQL standard][sql-standard] and other dialects. This crate

is used as a foundation for SQL query engines, vendor-specific

parsers, and various SQL analysis.



## Example



To parse a simple `SELECT` statement:



```rust

use sqlparser::dialect::GenericDialect;

use sqlparser::parser::Parser;



let sql = "SELECT a, b, 123, myfunc(b) \

           FROM table_1 \

           WHERE a > b AND b < 100 \

           ORDER BY a DESC, b";



let dialect = GenericDialect {}; // or AnsiDialect, or your own dialect ...



let ast = Parser::parse_sql(&dialect, sql).unwrap();



println!("AST: {:?}", ast);

```



This outputs



```rust

AST: [Query(Query { ctes: [], body: Select(Select { distinct: false, projection: [UnnamedExpr(Identifier("a")), UnnamedExpr(Identifier("b")), UnnamedExpr(Value(Long(123))), UnnamedExpr(Function(Function { name: ObjectName(["myfunc"]), args: [Identifier("b")], filter: None, over: None, distinct: false }))], from: [TableWithJoins { relation: Table { name: ObjectName(["table_1"]), alias: None, args: [], with_hints: [] }, joins: [] }], selection: Some(BinaryOp { left: BinaryOp { left: Identifier("a"), op: Gt, right: Identifier("b") }, op: And, right: BinaryOp { left: Identifier("b"), op: Lt, right: Value(Long(100)) } }), group_by: [], having: None }), order_by: [OrderByExpr { expr: Identifier("a"), asc: Some(false) }, OrderByExpr { expr: Identifier("b"), asc: None }], limit: None, offset: None, fetch: None })]

```



## Features



The following optional [crate  features](https://doc.rust-lang.org/cargo/reference/features.html) are available:



* `serde`: Adds [Serde](https://serde.rs/) support by implementing  `Serialize` and `Deserialize` for all AST nodes.

* `visitor`: Adds a `Visitor` capable of recursively walking the AST tree.



## Syntax vs Semantics



This crate provides only a syntax parser, and tries to avoid applying

any SQL semantics, and accepts queries that specific databases would

reject, even when using that Database's specific `Dialect`. For

example, `CREATE TABLE(x int, x int)` is accepted by this crate, even

though most SQL engines will reject this statement due to the repeated

column name `x`.



This crate avoids semantic analysis because it varies drastically

between dialects and implementations. If you want to do semantic

analysis, feel free to use this project as a base.



## Preserves Syntax Round Trip 



This crate allows users to recover the original SQL text (with comments removed,

normalized whitespace and keyword capitalization), which is useful for tools

that analyze and manipulate SQL.



This means that other than comments, whitespace and the capitalization of

keywords, the following should hold true for all SQL:



```rust

// Parse SQL

let ast = Parser::parse_sql(&GenericDialect, sql).unwrap();



// The original SQL text can be generated from the AST

assert_eq!(ast[0].to_string(), sql);

```



There are still some cases in this crate where different SQL with seemingly

similar semantics are represented with the same AST. We welcome PRs to fix such

issues and distinguish different syntaxes in the AST.



## SQL compliance



SQL was first standardized in 1987, and revisions of the standard have been

published regularly since. Most revisions have added significant new features to

the language, and as a result no database claims to support the full breadth of

features. This parser currently supports most of the SQL-92 syntax, plus some

syntax from newer versions that have been explicitly requested, plus some MSSQL,

PostgreSQL, and other dialect-specific syntax. Whenever possible, the [online

SQL:2016 grammar][sql-2016-grammar] is used to guide what syntax to accept.



Unfortunately, stating anything more specific about compliance is difficult.

There is no publicly available test suite that can assess compliance

automatically, and doing so manually would strain the project's limited

resources. Still, we are interested in eventually supporting the full SQL

dialect, and we are slowly building out our own test suite.



If you are assessing whether this project will be suitable for your needs,

you'll likely need to experimentally verify whether it supports the subset of

SQL that you need. Please file issues about any unsupported queries that you

discover. Doing so helps us prioritize support for the portions of the standard

that are actually used. Note that if you urgently need support for a feature,

you will likely need to write the implementation yourself. See the

[Contributing](#Contributing) section for details.



## Command line



This crate contains a CLI program that can parse a file and dump the results as JSON:

```

$ cargo run --features json_example --example cli FILENAME.sql [--dialectname]

```



## Users



This parser is currently being used by the [DataFusion] query engine,

[LocustDB], [Ballista], [GlueSQL], [Opteryx], [PRQL], [Qrlew], [JumpWire], and [ParadeDB].



If your project is using sqlparser-rs feel free to make a PR to add it

to this list.



## Design



The core expression parser uses the [Pratt Parser] design, which is a top-down

operator-precedence (TDOP) parser, while the surrounding SQL statement parser is

a traditional, hand-written recursive descent parser. Eli Bendersky has a good

[tutorial on TDOP parsers][tdop-tutorial], if you are interested in learning

more about the technique.



We are a fan of this design pattern over parser generators for the following

reasons:



- Code is simple to write and can be concise and elegant

- Performance is generally better than code generated by parser generators

- Debugging is much easier with hand-written code

- It is far easier to extend and make dialect-specific extensions

  compared to using a parser generator



### Supporting custom SQL dialects



This is a work in progress, but we have some notes on [writing a custom SQL

parser](docs/custom_sql_parser.md).



## Contributing



Contributions are highly encouraged! However, the bandwidth we have to

maintain this crate is limited. Please read the following sections carefully.



### New Syntax



The most commonly accepted PRs add support for or fix a bug in a feature in the

SQL standard, or a popular RDBMS, such as Microsoft SQL

Server or PostgreSQL, will likely be accepted after a brief

review.  Any SQL feature that is dialect specific should be parsed by *both* the relevant [`Dialect`] 

as well as [`GenericDialect`].



### Major API Changes



The current maintainers do not plan for any substantial changes to

this crate's API. PRs proposing major refactors

are not likely to be accepted.



### Testing



While we hope to review PRs in a reasonably

timely fashion, it may take a week or more. In order to speed the process,

please make sure the PR passes all CI checks, and includes tests

demonstrating your code works as intended (and to avoid

regressions). Remember to also test error paths.



PRs without tests will not be reviewed or merged.  Since the CI

ensures that `cargo test`, `cargo fmt`, and `cargo clippy`, pass you

should likely to run all three commands locally before submitting

your PR.



### Filing Issues



If you are unable to submit a patch, feel free to file an issue instead. Please

try to include:



  * some representative examples of the syntax you wish to support or fix;

  * the relevant bits of the [SQL grammar][sql-2016-grammar], if the syntax is

    part of SQL:2016; and

  * links to documentation for the feature for a few of the most popular

    databases that support it.



Unfortunately, if you need support for a feature, you will likely need to implement

it yourself, or file a well enough described ticket that another member of the community can do so.

Our goal as maintainers is to facilitate the integration

of various features from various contributors, but not to provide the

implementations ourselves, as we simply don't have the resources.



## Licensing



All code in this repository is licensed under the [Apache Software License 2.0](LICENSE.txt).



Unless you explicitly state otherwise, any contribution intentionally submitted

for inclusion in the work by you, as defined in the Apache-2.0 license, shall be

licensed as above, without any additional terms or conditions.



[tdop-tutorial]: https://eli.thegreenplace.net/2010/01/02/top-down-operator-precedence-parsing

[`cargo fmt`]: https://github.com/rust-lang/rustfmt#on-the-stable-toolchain

[current issues]: https://github.com/sqlparser-rs/sqlparser-rs/issues

[DataFusion]: https://github.com/apache/arrow-datafusion

[LocustDB]: https://github.com/cswinter/LocustDB

[Ballista]: https://github.com/apache/arrow-ballista

[GlueSQL]: https://github.com/gluesql/gluesql

[Opteryx]: https://github.com/mabel-dev/opteryx

[PRQL]: https://github.com/PRQL/prql

[Qrlew]: https://github.com/Qrlew/qrlew

[JumpWire]: https://github.com/extragoodlabs/jumpwire

[ParadeDB]: https://github.com/paradedb/paradedb

[Pratt Parser]: https://tdop.github.io/

[sql-2016-grammar]: https://jakewheat.github.io/sql-overview/sql-2016-foundation-grammar.html

[sql-standard]: https://en.wikipedia.org/wiki/ISO/IEC_9075

[`Dialect`]: https://docs.rs/sqlparser/latest/sqlparser/dialect/trait.Dialect.html

[`GenericDialect`]: https://docs.rs/sqlparser/latest/sqlparser/dialect/struct.GenericDialect.html