Struct lance_encoding::decoder::DecoderMiddlewareChainCursor

pub struct DecoderMiddlewareChainCursor<'a> { /* private fields */ }

A cursor into a decoder middleware chain

Each field scheduler is given a cursor during the create_field_scheduler call. This cursor can be used both to create child field schedulers and to create a scheduler from an inner encoding.

Implementations

impl<'a> DecoderMiddlewareChainCursor<'a>

pub fn current_path(&self) -> &VecDeque<u32>

Returns the current path into the field being decoded

pub fn io(&self) -> &Arc<dyn EncodingsIo>

Returns the I/O service which can be used to grab column metadata

pub fn next( self, field: &Field, column_infos: &mut VecDeque<ColumnInfo>, buffers: FileBuffers<'_>, ) -> Result<ChosenFieldScheduler<'a>>

Delegates responsibilty to the next encoder in the chain

Field schedulers should call this method when:

• They do not understand or handle the encoding
• They wrap an encoding and want a scheduler for the inner encoding

pub fn restart_at_current( self, field: &Field, column_infos: &mut VecDeque<ColumnInfo>, buffers: FileBuffers<'_>, ) -> Result<ChosenFieldScheduler<'a>>

Restarts the decoder chain without creating a new “child”

This can be useful, for example, when a field scheduler has an inner scheduler, and the current / parent strategies might apply to the inner scheduler.

If the current / parent strategies should not be consulted then call Self::next instead.

pub fn new_child( self, child_idx: u32, field: &Field, column_infos: &mut VecDeque<ColumnInfo>, buffers: FileBuffers<'_>, ) -> Result<ChosenFieldScheduler<'a>>

Restarts the decoder chain for a new “child” field. The main difference between this and Self::restart_at_current is that this method will modify Self::current_path