Struct RowSampler 

pub struct RowSampler<R = Vec<String>> { /* private fields */ }

Applies a SamplingStrategy to a stream of rows, holding the state the strategy needs across rows.

Engines create one sampler per scan and keep it for the whole scan.

R is what the fixed-size stage holds for each row until the stream ends. It is the row’s field values unless an engine has to keep something about the row that its values cannot say, and must then get it back with exactly the rows that were sampled.

Implementations

impl RowSampler

pub fn new(strategy: &SamplingStrategy) -> Result<Self, DataProfilerError>

Build a sampler for strategy.

impl<R> RowSampler<R>

pub fn for_rows(strategy: &SamplingStrategy) -> Result<Self, DataProfilerError>

As RowSampler::new, for a sampler whose fixed-size stage holds R for each row rather than its field values alone.

pub fn is_buffered(&self) -> bool

Whether rows must be handed to offer instead of being folded in as accept approves them.

pub fn is_noop(&self) -> bool

Whether this sampler can ever exclude a row.

pub fn accept(&mut self) -> bool

Decide whether the next row passes the systematic filter.

Call this for every row, including on the buffered path, so the row count stays exact.

pub fn offer(&mut self, values: R)

Hand a row that passed accept to the fixed-size stage.

Only meaningful when is_buffered is true.

pub fn take_sample(&mut self) -> Vec<R>

The final sample from the fixed-size stage, ready to fold into the statistics. Empty for a purely streaming strategy.

pub fn iterated_rows(&self) -> usize

Rows the sampler has seen, sampled or not.

pub fn sampled_rows(&self) -> usize

Rows that ended up in the sample.

Trait Implementations

impl<R: Debug> Debug for RowSampler<R>

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

Formats the value using the given formatter.