Trait VirtualTable 

pub trait VirtualTable: Send + Sync {
    type Cursor: VirtualTableCursor;

    // Required methods
    fn connect(cx: &Cx, args: &[&str]) -> Result<Self>
       where Self: Sized;
    fn best_index(&self, info: &mut IndexInfo) -> Result<()>;
    fn open(&self) -> Result<Self::Cursor>;

    // Provided methods
    fn create(cx: &Cx, args: &[&str]) -> Result<Self>
       where Self: Sized { ... }
    fn disconnect(&mut self, _cx: &Cx) -> Result<()> { ... }
    fn destroy(&mut self, cx: &Cx) -> Result<()> { ... }
    fn update(&mut self, _cx: &Cx, _args: &[SqliteValue]) -> Result<Option<i64>> { ... }
    fn begin(&mut self, _cx: &Cx) -> Result<()> { ... }
    fn sync_txn(&mut self, _cx: &Cx) -> Result<()> { ... }
    fn commit(&mut self, _cx: &Cx) -> Result<()> { ... }
    fn rollback(&mut self, _cx: &Cx) -> Result<()> { ... }
    fn rename(&mut self, _cx: &Cx, _new_name: &str) -> Result<()> { ... }
    fn savepoint(&mut self, _cx: &Cx, _n: i32) -> Result<()> { ... }
    fn release(&mut self, _cx: &Cx, _n: i32) -> Result<()> { ... }
    fn rollback_to(&mut self, _cx: &Cx, _n: i32) -> Result<()> { ... }
}

A virtual table module.

Virtual tables expose external data sources as SQL tables. This trait covers the full lifecycle: creation, connection, scanning, mutation, and destruction.

This trait is open (user-implementable). The Sized bound on constructor methods (create, connect) allows the trait to be used as dyn VirtualTable<Cursor = C> for other methods.

Default Implementations

Most methods have sensible defaults. At minimum, you must implement connect, best_index, and open.

Required Associated Types

type Cursor: VirtualTableCursor

The cursor type for scanning this virtual table.

Required Methods

fn connect(cx: &Cx, args: &[&str]) -> Result<Self>

where Self: Sized,

Called for subsequent opens of an existing virtual table.

fn best_index(&self, info: &mut IndexInfo) -> Result<()>

Inform the query planner about available indexes and their costs.

fn open(&self) -> Result<Self::Cursor>

Open a new scan cursor.

Provided Methods

fn create(cx: &Cx, args: &[&str]) -> Result<Self>

where Self: Sized,

Called for CREATE VIRTUAL TABLE.

May create backing storage. Default delegates to connect (suitable for eponymous virtual tables).

fn disconnect(&mut self, _cx: &Cx) -> Result<()>

Drop a virtual table instance (opposite of connect).

fn destroy(&mut self, cx: &Cx) -> Result<()>

Called for DROP VIRTUAL TABLE — destroy backing storage.

Default delegates to disconnect.

fn update(&mut self, _cx: &Cx, _args: &[SqliteValue]) -> Result<Option<i64>>

INSERT/UPDATE/DELETE on the virtual table.

• args[0]: old rowid (None for INSERT)
• args[1]: new rowid
• args[2..]: column values

Returns the new rowid for INSERT, None for UPDATE/DELETE.

Default returns FrankenError::ReadOnly (read-only virtual tables).

fn begin(&mut self, _cx: &Cx) -> Result<()>

Begin a virtual table transaction.

fn sync_txn(&mut self, _cx: &Cx) -> Result<()>

Sync a virtual table transaction (phase 1 of 2PC).

fn commit(&mut self, _cx: &Cx) -> Result<()>

Commit a virtual table transaction.

fn rollback(&mut self, _cx: &Cx) -> Result<()>

Roll back a virtual table transaction.

fn rename(&mut self, _cx: &Cx, _new_name: &str) -> Result<()>

Rename the virtual table.

Default returns FrankenError::Unsupported.

fn savepoint(&mut self, _cx: &Cx, _n: i32) -> Result<()>

Create a savepoint at level n.

fn release(&mut self, _cx: &Cx, _n: i32) -> Result<()>

Release savepoint at level n.

fn rollback_to(&mut self, _cx: &Cx, _n: i32) -> Result<()>

Roll back to savepoint at level n.

Implementors