actix-website/content/docs/databases.md

title	menu	weight
Databases	docs_patterns	1010

Async Options

We have several example projects showing use of async database adapters:

• Postgres: https://github.com/actix/examples/tree/master/databases/postgres
• SQLite: https://github.com/actix/examples/tree/master/databases/sqlite
• MongoDB: https://github.com/actix/examples/tree/master/databases/mongodb

Diesel

The current version of Diesel (v1) does not support asynchronous operations, so it is important to use the web::block function to offload your database operations to the Actix runtime thread-pool.

You can create action functions that correspond to all the operations your app will perform on the database.

{{< include-example example="databases" file="main.rs" section="handler" >}}

Now you should set up the database pool using a crate such as r2d2, which makes many DB connections available to your app. This means that multiple handlers can manipulate the DB at the same time, and still accept new connections. Simply, the pool in your app state. (In this case, it's beneficial not to use a state wrapper struct because the pool handles shared access for you.)

{{< include-example example="databases" file="main.rs" section="main" >}}

Now, in a request handler, use the Data<T> extractor to get the pool from app state and get a connection from it. This provides an owned database connection that can be passed into a web::block closure. Then just call the action function with the necessary arguments and .await the result.

This example also maps the error to an HttpResponse before using the ? operator but this is not necessary if your return error type implements ResponseError.

{{< include-example example="databases" file="main.rs" section="index" >}}

That's it! See the full example here: https://github.com/actix/examples/tree/master/databases/diesel