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() -> 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) -> &dyn FileReader

Returns the FileReader embedded in this Reader.

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 maybe_contains_key(&self, key: &K) -> bool

Asks the bloom filter of the reader if we have the key.

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.

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

where K: DataTrait + ?Sized, A: WeightTrait + ?Sized,

pub fn fetch_zset<'a, 'b>( &'a self, keys: &'b DynVec<K>, ) -> Result<FetchZSet<'a, 'b, K, A>, Error>

Returns a FetchZSet, which will subset this reader to just the rows in colunn 0 whose keys are in keys (which must be sorted) and return it as a Z-set, treating auxiliary values as weights.

impl<K0, A0, K1, A1> Reader<(&'static K0, &'static A0, (&'static K1, &'static A1, ()))>

where K0: DataTrait + ?Sized, A0: DataTrait + ?Sized, K1: DataTrait + ?Sized, A1: WeightTrait + ?Sized,

pub fn fetch_indexed_zset<'a, 'b>( &'a self, keys: &'b DynVec<K0>, ) -> Result<FetchIndexedZSet<'a, 'b, K0, A0, K1, A1>, Error>

Returns a FetchIndexedZSet, which will build an indexed Z-set from this reader containing just the rows whose keys are in keys (which must be sorted).

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.