Trait Backend 

pub trait Backend: Executor {
    // Required method
    fn begin<'life0, 'async_trait>(
        &'life0 self,
        isolation: Option<IsolationLevel>,
    ) -> Pin<Box<dyn Future<Output = Result<Box<dyn Transaction>, OrmError>> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait;

    // Provided methods
    fn read_parameter_count(
        &self,
        _plan: &QueryPlan,
    ) -> Result<Option<usize>, OrmError> { ... }
    fn begin_schema<'life0, 'async_trait>(
        &'life0 self,
        transactional: bool,
    ) -> Pin<Box<dyn Future<Output = Result<Box<dyn Transaction>, OrmError>> + Send + 'async_trait>>
       where Self: Sync + 'async_trait,
             'life0: 'async_trait { ... }
}

A connection pool that can open transactions.

Required Methods

fn begin<'life0, 'async_trait>( &'life0 self, isolation: Option<IsolationLevel>, ) -> Pin<Box<dyn Future<Output = Result<Box<dyn Transaction>, OrmError>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Begin a transaction on a dedicated connection.

isolation is validated against BackendCapabilities::isolation_levels before any I/O.

Provided Methods

fn read_parameter_count( &self, _plan: &QueryPlan, ) -> Result<Option<usize>, OrmError>

Count compiled read parameters without database I/O.

Args: _plan: Complete read plan whose existing binds consume capacity.

Returns: Exact compiled bind count, or None when the backend cannot report it. SQL prefetch requires this contract for bounded batching.

Errors

Capability or plan compilation errors.

fn begin_schema<'life0, 'async_trait>( &'life0 self, transactional: bool, ) -> Pin<Box<dyn Future<Output = Result<Box<dyn Transaction>, OrmError>> + Send + 'async_trait>>

where Self: Sync + 'async_trait, 'life0: 'async_trait,

Connection for a schema migration.

When transactional is true this is a transaction, same as begin with no isolation override. SQLite turns PRAGMA foreign_keys off on that connection before BEGIN (the pragma is a no-op inside a transaction), runs PRAGMA foreign_key_check before commit, and restores the previous pragma value afterwards. Other backends ignore the SQLite-specific work.

Errors

The default implementation has no way to hold a connection outside a transaction, so transactional == false fails with a capability error instead of silently handing back a transaction.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors