Struct Scan 

pub struct Scan { /* private fields */ }

One exact table scan with fixed options, metadata, and execution placement.

Implementations

impl Scan

pub fn identity(&self) -> TableIdentity

Immutable version read by this scan.

pub fn resolved_address(&self) -> Option<&ResourceAddress>

Canonical exact-version address inherited from a path-resolved Table. ID-only scans expose their provenance through Self::identity.

pub fn options(&self) -> &ScanOptions

Options fixed when the scan was opened.

pub fn schema(&self) -> SchemaRef

Projected schema, available without reading batches or performing I/O.

pub fn source_fields(&self) -> Option<&BTreeMap<String, Uuid>>

This method returns stable IDs for top-level stored columns, independent of the output projection. None marks scans without stable identities, such as change scans or scans from older hosts.

pub fn write_layout(&self) -> Option<&WriteLayout>

Preferred storage partitioning and clustering for writes to this exact table.

pub fn statistics(&self) -> Option<&ScanStatistics>

Stored statistics for this scan, with explicit exactness for counts and bounds.

pub fn ordering(&self) -> &[SortColumn]

Ordering guaranteed independently within each execution stream, with no global order.

pub fn filter_clauses(&self) -> &[FilterClause]

Exact support for the accepted predicate clauses.

pub fn estimated_rows(&self) -> Option<u64>

An estimate of the stored rows this scan reads, known without reading any rows.

It counts every row of the splits planning kept, so the scan’s filter, limit, or emit can return fewer rows. None when the plan does not estimate every split.

pub fn stream_count(&self) -> usize

Number of execution lanes available through Self::into_streams.

pub fn splits(&self) -> &[ScanSplit]

The splits planning kept, in stored order: the units of work that Self::read_work reads.

pub async fn read_work(&self, work: Vec<WorkItem>) -> Result<WorkStream, Error>

Read work in order, each item’s rows in stored order.

Each batch carries the index of its item in work and the stored row after the rows it covered, so a reader resumes an item from that row without reading any row twice. Items name splits of this scan by index and stored rows within them. Scans with a limit or an emit read no work items.

pub async fn count_rows(&self, work: &[WorkItem]) -> Result<Vec<u64>, Error>

The exact rows each item of work returns: stored rows that pass the filter and are not deleted. Counting reads only the filter’s columns, and none without a filter.

pub async fn take(&self, takes: Vec<Take>) -> Result<BatchStream, Error>

Read rows of this scan’s splits by position, in request order: each take’s rows in the order of its positions, a repeated position’s row again, the takes one after another.

This is the read a sampler calls: plan the scan once, count each split’s rows with Self::count_rows, then take the positions it draws. Each split’s rows are read in one pass, so positions that share storage share its reads, and takes beyond one request’s bounds are sent as several. A failed request is resumed from the rows it delivered. A position past its split fails the call before any rows are delivered. Scans with a filter, a limit or an emit take no rows.

pub fn into_stream(self) -> BatchStream

Consume the scan as one batch stream. Reading starts on first poll. Unordered options permit unordered output even when using one consumer.

pub fn into_streams(self) -> Vec<ScanStream>

Consume the scan as disjoint streams that together contain its selected rows.

Ordered lanes merge fixed groups of fragments when Self::ordering is nonempty. Other lanes share work dynamically. Consume all lanes concurrently for throughput. A global limit or explicit split yields one lane. Clone the scan, not a lane, to start a fresh execution without resolving metadata again. Dropping the last active lane cancels remaining work, including idle lanes.

pub fn into_narrowed_streams( self, filter: Arc<dyn SplitFilter>, ) -> Vec<ScanStream>

Self::into_streams, with each split narrowed by filter as it stands when the split opens.

Trait Implementations

impl Clone for Scan

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.