CODEWITHSUNDEEP
databaserustactix-webr2d2
porton
porton

Reputation: 5805

How to use DB connections in Actix several times per function?

At https://actix.rs/docs/databases/ there is an example:

async fn index(pool: web::Data<DbPool>, name: web::Path<(String)>) -> impl Responder {
    let name = name.into_inner();

    let conn = pool.get().expect("couldn't get db connection from pool");

    let user = web::block(move || actions::insert_new_user(&conn, &user))
        .await
        .map_err(|e| {
            eprintln!("{}", e);
            HttpResponse::InternalServerError().finish()
        })?;
    
    Ok(HttpResponse::Ok().json(user))
}

What to do if I need several SQL queries in one function? The following obviously won't work due to moving conn:

async fn index(pool: web::Data<DbPool>, name: web::Path<(String)>) -> impl Responder {
    let name = name.into_inner();

    let conn = pool.get().expect("couldn't get db connection from pool");

    let user1 = web::block(move || actions::insert_new_user(&conn, &user))
        .await
        .map_err(|e| {
            eprintln!("{}", e);
            HttpResponse::InternalServerError().finish()
        })?;

    // ... asynchronous code here

    let user2 = web::block(move || actions::insert_new_user(&conn, &user))
        .await
        .map_err(|e| {
            eprintln!("{}", e);
            HttpResponse::InternalServerError().finish()
        })?;
    
    Ok(HttpResponse::Ok().json(user))
}

I can receive several connections by repeated calls of pool.get(), but that inefficient to open a new SQL connection when one connection is enough.

So, how to deal with this?

Upvotes: 1

Views: 890

Answers (1)

Netwave
Netwave

Reputation: 42756

You just need to move the reference, not the connection itself:

async fn index(pool: web::Data<DbPool>, name: web::Path<(String)>) -> impl Responder {
    let name = name.into_inner();

    let conn_ = pool.get().expect("couldn't get db connection from pool");
    let conn = &conn_;
    let user1 = web::block(move || actions::insert_new_user(&conn, &user))
        .await
        .map_err(|e| {
            eprintln!("{}", e);
            HttpResponse::InternalServerError().finish()
        })?;

    // ... asynchronous code here

    let user2 = web::block(move || actions::insert_new_user(&conn, &user))
        .await
        .map_err(|e| {
            eprintln!("{}", e);
            HttpResponse::InternalServerError().finish()
        })?;
    
    Ok(HttpResponse::Ok().json(user))
}

Your problem can be reduced to (not working version):


struct Conn {}

fn foo(_: &Conn) {}


fn main() {

    let conn_ = Conn {};
    
    (move || foo(&conn_))();
    (move || foo(&conn_))();
    
}

Playground

Working version:

struct Conn {}

fn foo(_: &Conn) {}


fn main() {

    let conn_ = Conn {};
    let conn = &conn_;
    (move || foo(conn))();
    (move || foo(conn))();
    
}

Playground

Upvotes: 2

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