Trait Visitor 

pub trait Visitor {
    type Error: From<DecodeError>;
    type Row;

    // Required methods
    fn visit_insert<'a, R: BufReader<'a>>(
        &mut self,
        table_id: TableId,
        reader: &mut R,
    ) -> Result<Self::Row, Self::Error>;
    fn visit_delete<'a, R: BufReader<'a>>(
        &mut self,
        table_id: TableId,
        reader: &mut R,
    ) -> Result<Self::Row, Self::Error>;
    fn skip_row<'a, R: BufReader<'a>>(
        &mut self,
        table_id: TableId,
        reader: &mut R,
    ) -> Result<(), Self::Error>;

    // Provided methods
    fn visit_truncate(&mut self, _table_id: TableId) -> Result<(), Self::Error> { ... }
    fn visit_tx_start(&mut self, _offset: u64) -> Result<(), Self::Error> { ... }
    fn visit_tx_end(&mut self) -> Result<(), Self::Error> { ... }
    fn visit_inputs(&mut self, _inputs: &Inputs) -> Result<(), Self::Error> { ... }
    fn visit_outputs(&mut self, _outputs: &Outputs) -> Result<(), Self::Error> { ... }
}

A visitor useful to implement stateful super::Decoders of Txdata payloads.

Required Associated Types

type Error: From<DecodeError>

type Row

The type corresponding to one element in Ops::rowdata.

Required Methods

fn visit_insert<'a, R: BufReader<'a>>( &mut self, table_id: TableId, reader: &mut R, ) -> Result<Self::Row, Self::Error>

Called for each row in each Ops of a Mutations’ inserts.

The implementation is expected to determine the appropriate schema based on the supplied TableId, and to decode the row data from the supplied BufReader.

The reader’s position is assumed to be at the start of the next row after the method returns.

fn visit_delete<'a, R: BufReader<'a>>( &mut self, table_id: TableId, reader: &mut R, ) -> Result<Self::Row, Self::Error>

Called for each row in each Ops of a Mutations’ deletes.

Similar to Self::visit_insert, but allows the visitor to determine the start of the next section in a Mutations payload.

fn skip_row<'a, R: BufReader<'a>>( &mut self, table_id: TableId, reader: &mut R, ) -> Result<(), Self::Error>

Called to skip over rows from reader within a Mutations of a TX that should not be folded.

Takes &mut self because schema lookups may need mutable access to the visitor in order to memoize the computed schema. This method should not store or use the row in any way.

Provided Methods

fn visit_truncate(&mut self, _table_id: TableId) -> Result<(), Self::Error>

Called for each TableId encountered in the truncates section of a Mutations.

The default implementation does nothing.

fn visit_tx_start(&mut self, _offset: u64) -> Result<(), Self::Error>

Called for each Txdata record in a crate::Commit.

The default implementation does nothing.

fn visit_tx_end(&mut self) -> Result<(), Self::Error>

Called after each successful decode of a Txdata payload.

The default implementation does nothing.

fn visit_inputs(&mut self, _inputs: &Inputs) -> Result<(), Self::Error>

Called for each Inputs encountered in a Txdata payload.

The default implementation does nothing.

fn visit_outputs(&mut self, _outputs: &Outputs) -> Result<(), Self::Error>

Called for each Outputs encountered in a Txdata payload.

The default implementation does nothing.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors