postgres-named-parameters

postgres-named-parameters 是围绕 postgres 包的轻量级宏包装器，它为您的原始 SQL 查询提供了命名参数的便捷性。在底层，您的命名参数在编译时被转换成编号参数。

使用示例

use postgres_from_row::FromRow;
use postgres_named_parameters::Query;

// Use the postgres-from-row crate to decode each row returned
// from a query into a struct.
#[derive(FromRow, Debug)]
struct Person {
    first_name: String,
    last_name: String,
    hobby: Option<String>,
    alive: bool,
}

// Use a struct to define a query. The #[derive(Query)] will implement
// query functions that handle passing in the parameters, and the named
// parameters are converted to numbered parameters ($1, $2,...) at compile
// time.
#[derive(Query)]
#[query(
    // Write the query using named parameters
    sql = "
      SELECT *
      FROM Person
      WHERE (first_name = @name OR last_name = @name)
      AND alive = @alive",
    // Specify what type each row returned from the query should decode to
    row = Person
)]
struct GetPeople<'a> {
    // Define the query's parameters
    alive: bool,
    name: &'a str,
}

fn main() -> Result<(), postgres::Error> {
    let connection_string = std::env::var("POSTGRES_CONNECTION_STRING")
        .unwrap_or("host=localhost user=postgres".to_owned());
    let mut db = postgres::Client::connect(&connection_string, postgres::NoTls)?;

    // Execute the query
    let people: Vec<Person> = GetPeople {
        alive: true,
        name: "John",
    }
    .query_all(&mut db)?;

    // This roughly desugars to:
    //
    // let people: Vec<Person> = db.query(
    //     "SELECT *
    //      FROM Person
    //      WHERE (first_name = $2 OR last_name = $2)
    //      AND alive = $1",
    //     &[&true, &"John"],
    // )?
    // .iter()
    // .map(Person::try_from_row)
    // .collect::<Result<Vec<Person>,postgres::Error>>()?;
    //
    // Note that the #[derive(Query)] takes care of changing the SQL to use
    // numbered parameters (i.e. $1, $2) at compile time.

    println!("Found: {:?}", people);

    Ok(())
}

有关更详细的示例（包括批量查询），请参阅 GitHub 仓库中的示例项目文件夹：GitHub 仓库。

特性

• 支持事务
• SQL 转换为编号参数发生在编译时
• 输入命名参数错误（例如，将 @naame 而不是 @name）会在编译时产生错误

归属 & 相关库

本库受到了以下库的启发

• couch/aykroyd 提供了将查询表示为结构体的想法
• nolanderc/rust-postgres-query 和 solidsnack/rust-postgres-named-parameters 在创建 SQL 解析器时被用作参考
• 3noch/postgres-simple-interpolate 是启发创建 Rust 中处理 SQL 参数的便捷方式的 Haskell 库