[][src]Trait diesel::prelude::Connection

pub trait Connection: SimpleConnection + Sized + Send {
    type Backend: Backend;
    fn establish(database_url: &str) -> ConnectionResult<Self>;

    fn transaction<T, E, F>(&self, f: F) -> Result<T, E>
    where
        F: FnOnce() -> Result<T, E>,
        E: From<Error>
, { ... }
fn begin_test_transaction(&self) -> QueryResult<()> { ... }
fn test_transaction<T, E, F>(&self, f: F) -> T
    where
        F: FnOnce() -> Result<T, E>,
        E: Debug
, { ... } }

A connection to a database

Associated Types

type Backend: Backend

The backend this type connects to

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Required methods

fn establish(database_url: &str) -> ConnectionResult<Self>

Establishes a new connection to the database

The argument to this method varies by backend. See the documentation for that backend's connection class for details about what it accepts.

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Provided methods

fn transaction<T, E, F>(&self, f: F) -> Result<T, E> where
    F: FnOnce() -> Result<T, E>,
    E: From<Error>, 

Executes the given function inside of a database transaction

If there is already an open transaction, savepoints will be used instead.

If the transaction fails to commit due to a SerializationFailure or a ReadOnlyTransaction a rollback will be attempted. If the rollback succeeds, the original error will be returned, otherwise the error generated by the rollback will be returned. In the second case the connection should be considered broken as it contains a uncommitted unabortable open transaction.

Example

use diesel::result::Error;

conn.transaction::<_, Error, _>(|| {
    diesel::insert_into(users)
        .values(name.eq("Ruby"))
        .execute(&conn)?;

    let all_names = users.select(name).load::<String>(&conn)?;
    assert_eq!(vec!["Sean", "Tess", "Ruby"], all_names);

    Ok(())
})?;

conn.transaction::<(), _, _>(|| {
    diesel::insert_into(users)
        .values(name.eq("Pascal"))
        .execute(&conn)?;

    let all_names = users.select(name).load::<String>(&conn)?;
    assert_eq!(vec!["Sean", "Tess", "Ruby", "Pascal"], all_names);

    // If we want to roll back the transaction, but don't have an
    // actual error to return, we can return `RollbackTransaction`.
    Err(Error::RollbackTransaction)
});

let all_names = users.select(name).load::<String>(&conn)?;
assert_eq!(vec!["Sean", "Tess", "Ruby"], all_names);

fn begin_test_transaction(&self) -> QueryResult<()>

Creates a transaction that will never be committed. This is useful for tests. Panics if called while inside of a transaction.

fn test_transaction<T, E, F>(&self, f: F) -> T where
    F: FnOnce() -> Result<T, E>,
    E: Debug

Executes the given function inside a transaction, but does not commit it. Panics if the given function returns an error.

Example

use diesel::result::Error;

conn.test_transaction::<_, Error, _>(|| {
    diesel::insert_into(users)
        .values(name.eq("Ruby"))
        .execute(&conn)?;

    let all_names = users.select(name).load::<String>(&conn)?;
    assert_eq!(vec!["Sean", "Tess", "Ruby"], all_names);

    Ok(())
});

// Even though we returned `Ok`, the transaction wasn't committed.
let all_names = users.select(name).load::<String>(&conn)?;
assert_eq!(vec!["Sean", "Tess"], all_names);
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Implementors

impl Connection for MysqlConnection[src]

impl Connection for PgConnection[src]

impl Connection for SqliteConnection[src]

impl<M> Connection for PooledConnection<M> where
    M: ManageConnection,
    M::Connection: Connection + R2D2Connection + Send + 'static, 
[src]

type Backend = <M::Connection as Connection>::Backend

type TransactionManager = PooledConnectionTransactionManager<M>

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