Struct Scanner

pub struct Scanner { /* private fields */ }

Represents a scan operation to read data from a set of rows, with an optional filter expression, and a projection expression.

A scan operation can be broken into many RangeScanner operations, each of which leverages shared statistics from the parent Scanner to optimize the order in which filter and projection operations are applied.

For example, if a filter expression has a top-level AND clause, it may be the case that one clause is significantly more selective than the other. In this case, we may want to compute the most selective filter first, then prune rows using result of the filter, before evaluating the second filter over the reduced set of rows.

Implementations

impl Scanner

pub fn new( dtype: DType, projection: ExprRef, filter: Option<ExprRef>, ) -> VortexResult<Self>

Create a new scan with the given projection and optional filter.

pub fn projection(&self) -> &ExprRef

Returns the projection expression.

pub fn result_dtype(&self) -> &DType

Compute the result dtype of the scan given the input dtype.

pub fn range_scanner( self: Arc<Self>, row_mask: RowMask, ) -> VortexResult<RangeScanner>

Instantiate a new scan for a specific range. The range scan will share statistics with this parent scan in order to optimize future range scans.

Trait Implementations

impl Clone for Scanner

fn clone(&self) -> Scanner

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Scanner

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

Formats the value using the given formatter.