Transaction

A transaction is a group of SQL statements executed with ACID guarantee. There are two transaction APIs.

Within a Closure

The transaction will be committed if the closure returned Ok, rollbacked if returned Err. The 2nd and 3rd type parameters are the Ok and Err types respectively.

// <Fn, A, B> -> Result<A, B>
db.transaction::<_, (), DbErr>(|txn| {
    Box::pin(async move {
        bakery::ActiveModel {
            name: Set("SeaSide Bakery".to_owned()),
            profit_margin: Set(10.4),
            ..Default::default()
        }
        .save(txn)
        .await?;

        bakery::ActiveModel {
            name: Set("Top Bakery".to_owned()),
            profit_margin: Set(15.0),
            ..Default::default()
        }
        .save(txn)
        .await?;

        Ok(())
    })
})
.await;

This is the preferred way for most cases. However, if you happen to run into an impossible lifetime while trying to capture a reference in the async block, then the following API is the solution.

begin & commit / rollback

begin the transaction followed by a commit or rollback. If txn goes out of scope, the transaction is automatically rollbacked.

let txn = db.begin().await?;

bakery::ActiveModel {
    name: Set("SeaSide Bakery".to_owned()),
    profit_margin: Set(10.4),
    ..Default::default()
}
.save(&txn)
.await?;

bakery::ActiveModel {
    name: Set("Top Bakery".to_owned()),
    profit_margin: Set(15.0),
    ..Default::default()
}
.save(&txn)
.await?;

txn.commit().await?;