Crate include_postgres_sql

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include-postgres-sql is an extension of include-sql for using Postgres SQL in Rust. It completes include-sql by providing impl_sql macro to generate database access methods from the included SQL. include-postgres-sql uses Rust-Postgres for database access.

Features

include-postgres-sql has a single feature - tokio - which, when selected, makes include-postgres-sql generate async databases access methods that can be used with tokio-postgres.

Usage

Add include-postgres-sql and postgres as a dependency:

[dependencies]
include-postgres-sql = "0.1"
postgres = "0.19"

Write your SQL and save it in a file. For example, let’s say the following is the content of the library.sql file that is saved in the project’s src folder:

-- name: get_loaned_books?
-- Returns the list of books loaned to a patron
-- # Parameters
-- param: user_id: &str - user ID
SELECT book_title
  FROM library
 WHERE loaned_to = :user_id
 ORDER BY 1;

-- name: loan_books!
-- Updates the book records to reflect loan to a patron
-- # Parameters
-- param: user_id: &str - user ID
-- param: book_ids: i32 - book IDs
UPDATE library
   SET loaned_to = :user_id
     , loaned_on = current_timestamp
 WHERE book_id IN (:book_ids);

And then use it in Rust as:

ⓘ
use include_postgres_sql::{include_sql, impl_sql};
use postgres::{Config, NoTls, Error};

include_sql!("src/library.sql");

fn main() -> Result<(),Error> {
    let args : Vec<String> = std::env::args().collect();
    let user_id = &args[1];

    let mut db = Config::new().host("localhost").connect(NoTls)?;

    db.get_loaned_books(user_id, |row| {
        let book_title : &str = row.try_get("book_title")?;
        println!("{}", book_title);
        Ok(())
    })?;

    Ok(())
}

Note that the path to the SQL file must be specified relative to the project root, i.e. relative to CARGO_MANIFEST_DIR, even if you keep your SQL file alongside rust module that includes it. Because include-sql targets stable Rust this requirement will persist until SourceFile stabilizes.

Async

Add the following dependencies:

[dependencies]
include-postgres-sql = { version = "0.1", features = ["tokio"] }
tokio-postgres = "0.7"
tokio = { version = "1", features = ["full"] }

Note full tokio features are not required. This dependency is listed like that for illustration only.

The same SQL as above can then be used in async Rust as:

ⓘ
use include_postgres_sql::{include_sql, impl_sql};
use tokio_postgres::{Config, NoTls, Error};

include_sql!("src/library.sql");

#[tokio::main]
fn main() -> Result<(),Error> {
    let args : Vec<String> = std::env::args().collect();
    let user_id = &args[1];

    let (db, conn) = Config::new().host("localhost").connect(NoTls).await?;
    tokio::spawn(async move {
        if let Err(e) = conn.await {
            eprintln!("connection error: {}", e);
        }
    });

    db.get_loaned_books(user_id, |row| {
        let book_title : &str = row.try_get("book_title")?;
        println!("{}", book_title);
        Ok(())
    }).await?;

    Ok(())
}

Anatomy of the Included SQL File

Please see the Anatomy of the Included SQL File in include-sql documentation for the description of the format that include-sql can parse.

Generated Methods

include-postgres-sql generates 3 variants of database access methods using the following selectors:

  • ? - methods that process rows retrieved by SELECT,
  • ! - methods that execute all other non-SELECT methods, and
  • -> - methods that execute RETURNING statements and provide access to returned data.

Process Selected Rows

For the SELECT statement like:

-- name: get_loaned_books?
-- param: user_id: &str
SELECT book_title FROM library WHERE loaned_to = :user_id;

The method with the following signature is generated:

ⓘ
fn get_loaned_books<F>(&self, user_id: &str, row_callback: F) -> Result<(),postgres::Error>
where F: Fn(postgres::Row) -> Result<(),postgres::Error>;

Where:

  • user_id is a parameter that has the same name as the SQL parameter with the declared (in the SQL) type as &str.
  • F is a type of a callback (closure) that the method implementation will call to process each row.

Execute Non-Select Statements

For non-select statements - INSERT, UPDATE, DELETE, etc. - like the following:

-- name: loan_books!
-- param: user_id: &str
-- param: book_ids: i32
UPDATE library
   SET loaned_to = :user_id
     , loaned_on = current_timestamp
 WHERE book_id IN (:book_ids);

The method with the following signature is generated:

ⓘ
fn loan_books(&self, user_id: &str, book_ids: &[i32]) -> Result<u64,postgres::Error>;

Where:

  • user_id is a parameter that has the same name as the SQL parameter with the declared (in the SQL) type as &str,
  • book_ids is a parameter for the matching IN-list parameter where each item in a collection has type u32.

RETURNING Statements

For DELETE, INSERT, and UPDATE statements that return data via RETURNING clause like:

-- name: add_new_book->
-- param: isbn: &str
-- param: book_title: &str
INSERT INTO library (isbn, book_title)
VALUES (:isbn, :book_title)
RETURNING book_id;

The method with the following signature is generated:

ⓘ
fn add_new_book(&self, isbn: &str, book_title: &str) -> Result<postgres::Row,postgres::Error>;

Inferred Parameter Types

If a statement parameter type is not explicitly specified via param:, include-postgres-sql will use impl postgres::types::ToSql for the corresponding scalar method parameters. For example, if the SQL from the example above has not provided its parameter type:

-- name: get_loaned_books?
SELECT book_title
  FROM library
 WHERE loaned_to = :user_id
 ORDER BY 1;

Then the signature of the generated method would be:

ⓘ
fn get_loaned_books<F>(&self, user_id: impl postgres::types::ToSql, row_callback: F) -> Result<(),postgres::Error>
where F: Fn(postgres::Row) -> Result<(),postgres::Error>;

For the “IN list” type of parameters include-postgres-sql will generate a method parameter as a slice where each element is the same generic type supplied by include-sql:

-- name: loan_books!
UPDATE library
   SET loaned_to = :user_id
     , loaned_on = current_timestamp
 WHERE book_id IN (:book_ids);

The signature of the generated method would be:

ⓘ
fn loan_books<BookIds: postgres::types::ToSql>(&self, user_id: impl postgres::types::ToSql, book_ids: &[BookIds]) -> Result<u64,postgres::Error>;

Macros

impl_sql

Generates Rust code to use included SQL.

include_sql

Reads and parses the specified SQL file, and generates impl_sql macro call.