Struct TransactionBuilder

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pub struct TransactionBuilder<'a, C> { /* private fields */ }

Available on crate feature postgres_backend only.

Expand description

Used to build a transaction, specifying additional details.

This struct is returned by .build_transaction. See the documentation for methods on this struct for usage examples. See the PostgreSQL documentation for SET TRANSACTION for details on the behavior of each option.

Implementations§

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impl<'a, C> TransactionBuilder<'a, C>
where C: Connection<Backend = Pg, TransactionManager = AnsiTransactionManager>,

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pub fn new(connection: &'a mut C) -> Self

Available on crate feature i-implement-a-third-party-backend-and-opt-into-breaking-changes only.

Creates a new TransactionBuilder.

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pub fn read_only(self) -> Self

Makes the transaction READ ONLY

§Example

conn.build_transaction()
    .read_only()
    .run::<_, diesel::result::Error, _>(|conn| {
        let read_attempt = users.select(name).load::<String>(conn);
        assert!(read_attempt.is_ok());

        let write_attempt = diesel::insert_into(users)
            .values(name.eq("Ruby"))
            .execute(conn);
        assert!(write_attempt.is_err());

        Ok(())
    })?;

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pub fn read_write(self) -> Self

Makes the transaction READ WRITE

This is the default, unless you’ve changed the default_transaction_read_only configuration parameter.

§Example

conn.build_transaction()
    .read_write()
    .run(|conn| {
        let read_attempt = users.select(name).load::<String>(conn);
        assert!(read_attempt.is_ok());

        let write_attempt = diesel::insert_into(users)
            .values(name.eq("Ruby"))
            .execute(conn);
        assert!(write_attempt.is_ok());

        Ok(())
    })

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pub fn deferrable(self) -> Self

Makes the transaction DEFERRABLE

§Example

conn.build_transaction()
    .deferrable()
    .run(|conn| Ok(()))

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pub fn not_deferrable(self) -> Self

Makes the transaction NOT DEFERRABLE

This is the default, unless you’ve changed the default_transaction_deferrable configuration parameter.

§Example

conn.build_transaction()
    .not_deferrable()
    .run(|conn| Ok(()))

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pub fn read_committed(self) -> Self

Makes the transaction ISOLATION LEVEL READ COMMITTED

This is the default, unless you’ve changed the default_transaction_isolation_level configuration parameter.

§Example

conn.build_transaction()
    .read_committed()
    .run(|conn| Ok(()))

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pub fn repeatable_read(self) -> Self

Makes the transaction ISOLATION LEVEL REPEATABLE READ

§Example

conn.build_transaction()
    .repeatable_read()
    .run(|conn| Ok(()))

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pub fn serializable(self) -> Self

Makes the transaction ISOLATION LEVEL SERIALIZABLE

§Example

conn.build_transaction()
    .serializable()
    .run(|conn| Ok(()))

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pub fn run<T, E, F>(&mut self, f: F) -> Result<T, E>
where F: FnOnce(&mut C) -> Result<T, E>, E: From<Error>,

Runs the given function inside of the transaction with the parameters given to this builder.

This function executes the provided closure f inside a database transaction. If there is already an open transaction for the current connection it will return an error. The connection is committed if the closure returns Ok(_), it will be rolled back if it returns Err(_). For both cases the original result value will be returned from this function.

If the transaction fails to commit and requires a rollback according to Postgres, (e.g. serialization failure) a rollback will be attempted. If the rollback fails, the error will be returned in a Error::RollbackErrorOnCommit, from which you will be able to extract both the original commit error and the rollback error. In addition, the connection will be considered broken as it contains a uncommitted unabortable open transaction. Any further interaction with the transaction system will result in an returned error in this case.