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48 lines
2.0 KiB
Markdown
48 lines
2.0 KiB
Markdown
---
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title: Databases
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menu: docs_patterns
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weight: 1010
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---
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# Async Options
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We have several example projects showing use of async database adapters:
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- Postgres: https://github.com/actix/examples/tree/master/databases/postgres
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- SQLite: https://github.com/actix/examples/tree/master/databases/sqlite
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- MongoDB: https://github.com/actix/examples/tree/master/databases/mongodb
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# Diesel
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The current version of Diesel (v1) does not support asynchronous operations, so it is important to
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use the [`web::block`][web-block] function to offload your database operations to the Actix runtime
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thread-pool.
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You can create action functions that correspond to all the operations your app will perform on the
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database.
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{{< include-example example="databases" file="main.rs" section="handler" >}}
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Now you should set up the database pool using a crate such as `r2d2`, which makes many DB
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connections available to your app. This means that multiple handlers can manipulate the DB at the
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same time, and still accept new connections. Simply, the pool in your app state. (In this case, it's
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beneficial not to use a state wrapper struct because the pool handles shared access for you.)
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{{< include-example example="databases" file="main.rs" section="main" >}}
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Now, in a request handler, use the `Data<T>` extractor to get the pool from app state and get a
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connection from it. This provides an owned database connection that can be passed into a
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[`web::block`][web-block] closure. Then just call the action function with the necessary arguments
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and `.await` the result.
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This example also maps the error to an `HttpResponse` before using the `?` operator but this is not
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necessary if your return error type implements [`ResponseError`][response-error].
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{{< include-example example="databases" file="main.rs" section="index" >}}
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That's it! See the full example here:
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https://github.com/actix/examples/tree/master/databases/diesel
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[web-block]: https://docs.rs/actix-web/3/actix_web/web/fn.block.html
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[response-error]: https://docs.rs/actix-web/3/actix_web/trait.ResponseError.html
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