Struct Reader 

pub struct Reader<T> { /* private fields */ }

Layer file reader.

T in Reader<T> must be a ColumnSpec that specifies the key and auxiliary data types for all of the columns in the file to be read.

Use Reader::rows to read data.

Implementations

impl<T> Reader<T>

where T: ColumnSpec,

pub fn mark_for_checkpoint(&self)

Marks the file of the reader as being part of a checkpoint.

pub fn open( factories: &[&AnyFactories], cache: fn() -> Option<Arc<BufferCache>>, storage_backend: &dyn StorageBackend, path: &StoragePath, ) -> Result<Self, Error>

Instantiates a reader given an existing path.

pub fn n_columns(&self) -> usize

The number of columns in the layer file.

This is a fixed value for any given Reader.

pub fn n_rows(&self, column: usize) -> u64

The number of rows in the given column.

For column 0, this is the number of rows that may be visited with rows. In other columns, it is the number of rows that may be visited in total by calling next_column() on each of the rows in the previous column.

pub fn path(&self) -> &StoragePath

Returns the storage path for the underlying object.

pub fn byte_size(&self) -> Result<u64, Error>

Returns the size of the underlying file in bytes.

pub fn cache_stats(&self) -> CacheStats

Returns the cache statistics for this file. The statistics are specific to this file’s cache behavior for reads.

pub fn file_handle(&self) -> &Arc<dyn FileReader>

Returns the FileReader embedded in this Reader.

pub fn metadata(&self) -> &BatchMetadata

Returns additional metadata added to the file by the writer.

impl<K, A, N> Reader<(&'static K, &'static A, N)>

where K: DataTrait + ?Sized, A: DataTrait + ?Sized, (&'static K, &'static A, N): ColumnSpec,

pub fn membership_filter(&self) -> Result<Option<BatchKeyFilter>, Error>

Reads and deserializes the per-batch membership filter, if present.

For roaring filters this also threads the batch minimum into the min-offset decoder, so the returned filter can be queried directly.

pub fn key_range(&self) -> Result<Option<(Box<K>, Box<K>)>, Error>

Returns the min and max keys stored in column 0.

The bounds are loaded from the root node when first requested and can then be cached by higher-level batch types.

pub fn rows(&self) -> RowGroup<'_, K, A, N, (&'static K, &'static A, N)>

Returns a RowGroup for all of the rows in column 0.

pub fn bulk_rows( &self, ) -> Result<BulkRows<'_, K, A, N, (&'static K, &'static A, N)>, Error>

Returns a BulkRows for column 0.

Trait Implementations

impl<T: Debug> Debug for Reader<T>

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

Formats the value using the given formatter.

impl<K, A, N> FallibleEq for Reader<(&'static K, &'static A, N)>

where K: DataTrait + ?Sized, A: DataTrait + ?Sized, (&'static K, &'static A, N): ColumnSpec, for<'a> RowGroup<'a, K, A, N, (&'static K, &'static A, N)>: FallibleEq,

fn equals(&self, other: &Self) -> Result<bool, Error>

Compares self to other and returns whether they are equal, with the possibility of failure due to an I/O error.

impl<T> SizeOf for Reader<T>

where T: ColumnSpec,

fn size_of_children(&self, context: &mut Context)

Gets the size of all “children” owned by this value, not including the size of the value itself.

fn size_of(&self) -> TotalSize

Gets the total size of the current value

fn size_of_with_context(&self, context: &mut Context)

Adds the size of the current value to the given Context, including both the size of the value itself and all of its children