Struct Reader 

pub struct Reader { /* private fields */ }

Reads committed native column pages without holding the table in memory.

Implementations

impl Reader

pub fn open(path: impl AsRef<Path>) -> Result<Self>

Opens the highest valid directory slot.

Errors

If the file has no valid committed directory or a directory pointer is out of bounds.

pub fn table(&self) -> &Table

The committed table directory.

pub fn top_frequencies( &self, column: usize, top: usize, ) -> Result<Option<Vec<(Value, u64)>>>

Exact leading frequencies when the stored synopsis proves a count-descending prefix.

The returned list can be longer than top. Keeping the stored tail lets a later TopN apply additional ordering keys without losing a value tied with the requested boundary.

Errors

If the column is outside the schema or a stored value does not fit its declared type.

pub fn frequency_occurrences( &self, column: usize, ) -> Result<Option<FrequencyOccurrences>>

Sparse rows belonging to the bounded numeric frequency candidate set.

The list is omitted when collecting it would exceed the fixed storage budget. A composite aggregate may accept a result over these rows only when its requested boundary is strictly greater than omitted_max.

Errors

If the column is outside the schema.

pub fn read(&self, stripe: usize, columns: &[usize]) -> Result<Chunk>

Reads only the named columns from one stripe.

Errors

If a stripe, column, page, or checksum is invalid.

pub fn read_sparse(&self, stripe: usize, columns: &[usize]) -> Result<Chunk>

Reads named columns from one stripe without prefetching adjacent stripe pages.

This is intended for sparse row fetches after a selective TopN or filter. Sequential scans should use Self::read so adjacent pages share one extent read.

Errors

If a stripe, column, page, or checksum is invalid.

pub fn skips_codes( &self, stripe: usize, column: usize, candidates: &[u32], ) -> Result<bool>

Whether an exact global-code membership index proves that a stripe cannot contain any of the sorted candidate codes.

A file written before v8 has no membership index and conservatively keeps the stripe.

Errors

If the stripe, column, index page, checksum, or delta stream is invalid.

pub fn skips(&self, stripe: usize, probes: &[Probe]) -> bool

Whether persisted bounds prove that a stripe cannot match the predicates.

Trait Implementations

impl Clone for Reader

fn clone(&self) -> Reader

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Reader

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

Formats the value using the given formatter.