Struct FileReader 

pub struct FileReader { /* private fields */ }

A current-format Lance file reader backed by fully decoded metadata.

Implementations

impl FileReader

pub fn with_scheduler(&self, scheduler: Arc<dyn EncodingsIo>) -> Self

pub fn with_io_stats(&self, stats: Arc<dyn IoStatsRecorder>) -> Self

Returns a clone of this reader whose I/O is additionally recorded into stats, on top of the scheduler’s global accounting.

All cached metadata is shared with self, so no file is re-opened and only a few Arc clones are performed. If the underlying I/O service does not support per-scope statistics (e.g. an in-memory scheduler), the returned reader is an ordinary, uninstrumented clone.

pub fn num_rows(&self) -> u64

pub fn column_num_rows(&self, column_index: usize) -> Result<u64>

The number of rows stored in a single physical column.

For ordinary (rectangular) files every column has the same length, equal to num_rows. Files written with FileWriter::write_column may have columns of differing lengths; this returns the length of one such column, derived by summing its pages’ row counts. Errors if column_index is out of bounds.

pub fn metadata(&self) -> &Arc<CachedFileMetadata>

pub fn file_statistics(&self) -> FileStatistics

pub async fn read_global_buffer(&self, index: u32) -> Result<Bytes>

pub fn schema(&self) -> &Arc<Schema>

impl FileReader

pub async fn try_open( scheduler: FileScheduler, base_projection: Option<ReaderProjection>, decoder_plugins: Arc<DecoderPlugins>, cache: &LanceCache, options: FileReaderOptions, ) -> Result<Self>

pub async fn try_open_with_file_metadata( scheduler: Arc<dyn EncodingsIo>, path: Path, base_projection: Option<ReaderProjection>, decoder_plugins: Arc<DecoderPlugins>, metadata: Arc<CachedFileMetadata>, cache: &LanceCache, options: FileReaderOptions, ) -> Result<Self>

pub async fn read_all_metadata( scheduler: &FileScheduler, ) -> Result<CachedFileMetadata>

pub async fn read_metadata_index( scheduler: &FileScheduler, ) -> Result<FileMetadataIndex>

pub async fn read_metadata_index_with_schema( scheduler: &FileScheduler, file_schema: Arc<Schema>, num_rows: u64, ) -> Result<FileMetadataIndex>

pub fn version(&self) -> ConcreteFileVersion

pub async fn read_tasks( &self, params: ReadBatchParams, batch_size: u32, projection: Option<ReaderProjection>, filter: FilterExpression, ) -> Result<Pin<Box<dyn Stream<Item = ReadBatchTask> + Send>>>

pub async fn read_stream_projected( &self, params: ReadBatchParams, batch_size: u32, batch_readahead: u32, projection: ReaderProjection, filter: FilterExpression, ) -> Result<Pin<Box<dyn RecordBatchStream>>>

pub fn read_stream_projected_blocking( &self, params: ReadBatchParams, batch_size: u32, projection: Option<ReaderProjection>, filter: FilterExpression, ) -> Result<Box<dyn RecordBatchReader + Send + 'static>>

pub async fn read_stream( &self, params: ReadBatchParams, batch_size: u32, batch_readahead: u32, filter: FilterExpression, ) -> Result<Pin<Box<dyn RecordBatchStream>>>

Trait Implementations

impl Clone for FileReader

fn clone(&self) -> FileReader

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FileReader

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.