Struct ScanRequest 

pub struct ScanRequest {
    pub projection: Expression,
    pub filter: Option<Expression>,
    pub row_range: Option<Range<u64>>,
    pub selection: Selection,
    pub partition_selection: Selection,
    pub partition_range: Option<Range<u64>>,
    pub ordered: bool,
    pub limit: Option<u64>,
}

A request to scan a data source.

Fields

projection: Expression

Projection expression. Defaults to root() which returns all columns.

filter: Option<Expression>

Filter expression, None implies no filter.

row_range: Option<Range<u64>>

The per-partition row range to read. Row range will be applied over every partition you scan.

selection: Selection

The per-partition row selection to read. Row selection will be applied over every partition you scan.

partition_selection: Selection

Partition selection to scan, which allows readers to skip unwanted partitions.

partition_range: Option<Range<u64>>

Partition range to scan, which allows readers to skip unwanted partitions.

ordered: bool

Whether the scan should preserve row order. If false, the scan may produce rows in any order, for example to enable parallel execution across partitions.

limit: Option<u64>

Optional limit on the number of rows returned, applied after filtering and row selection.

For an unordered scan the limit is global: partitions share one budget, so together they return no more than limit rows. An ordered scan cannot share a budget whose reservation order is completion order, so each partition applies the limit locally and the caller must trim the concatenated result.

Trait Implementations

impl Clone for ScanRequest

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ScanRequest

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

Formats the value using the given formatter.

impl Default for ScanRequest

fn default() -> Self

Returns the “default value” for a type.