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This post is auto-generated from RSS feed The Rust Programming Language Forum - Latest topics. Source: Sqlx transaction abstraction

Hi, yall.

So I've been recently working with sqlx and I'm trying to figure out how to abstract queries over connections/transactions. What I wanted to have is a service that manages transactions and a dao that runs the sql statements. I got it to work, however I don't like my abstractions particularly much.

What I would have is a TransactionProvider like PgPool that service can use to execute commands.

pub struct SomeService<Provider> {
    transactionManager: Provider,
}

impl<Provider: TransactionProvider> SomeService<Provider> {
    pub async fn run_raw(&self) {
        run_query(self.transactionManager.connection()).await;
    }

    pub async fn run_in_transaction(&self) {
        let mut transaction = self.transactionManager.transaction().await;
        run_query(transaction.get()).await;
        run_query(transaction.get()).await;
        transaction.commit().await.unwrap();
    }
}

async fn run_query<'a, A>(a: A) -> ()
where
    A: Acquire<'a, Database = Postgres> + Send + Sync,
{
    let mut executor = a.acquire().await.unwrap();
    sqlx::query("select 'hello world'")
        .execute(&mut *executor)
        .await
        .unwrap();
}

This is a simplified version. I would actually have a Dao instead of functions directly, but the idea is the same. I either use connection directly through self.transaction.connection() or in a transaction through self.transactionManager.transaction().

To create this I would use TransactionProvider which is a simple wrapper over PgPool basic operations.

pub trait TransactionProvider {
    type BasicConnection<'a>: Acquire<'a, Database = Postgres> + Send + Sync
    where
        Self: 'a;
    type Transaction: GenericTransaction + Send + Sync;

    fn connection<'a>(&'a self) -> Self::BasicConnection<'a>;

    async fn transaction<'a>(&'a self) -> Self::Transaction;
}

impl TransactionProvider for PgPool {
    type BasicConnection<'a> = &'a PgPool;
    type Transaction = Transaction<'static, Postgres>;

    fn connection<'a>(&'a self) -> Self::BasicConnection<'a> {
        self
    }

    async fn transaction<'a>(&'a self) -> Self::Transaction {
        self.begin().await.unwrap()
    }
}

pub trait GenericTransaction {
    type Connection<'a>: Acquire<'a, Database = Postgres> + Send + Sync
    where
        Self: 'a;

    fn get<'a>(&'a mut self) -> Self::Connection<'a>;

    async fn commit(self) -> Result<(), sqlx::Error>;

    async fn rollback(self) -> Result<(), sqlx::Error>;
}

impl GenericTransaction for Transaction<'static, Postgres> {
    type Connection<'a>
        = &'a mut Self
    where
        Self: 'a;

    fn get<'a>(&'a mut self) -> Self::Connection<'a> {
        self
    }

    async fn commit(self) -> Result<(), sqlx::Error> {
        self.commit().await
    }

    async fn rollback(self) -> Result<(), sqlx::Error> {
        self.rollback().await
    }
}

The issue is that it's a lot of work and it's not the best in terms of DX.

Has anyone figured out a better way? Or a better logic separation that works with sqxl?

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