Struct SamplingState 

pub struct SamplingState { /* private fields */ }

The cross-row state that stateful strategies need.

One instance lives for a whole scan. Recreating it per row — which is what a stateless helper amounts to — makes every stateful strategy behave as if each row were the first, which is how stratified sampling came to return nothing and reservoir sampling came to return everything.

Implementations

impl SamplingState

pub fn new() -> Self

pub fn progressive_taken(&self) -> usize

Rows a Progressive stage has taken so far.

pub fn record_progressive(&mut self)

Record that a Progressive stage took a row.

pub fn take_from_stratum( &mut self, row: RowView<'_>, key_columns: &[String], samples_per_stratum: usize, ) -> bool

Take row for its stratum if that stratum still has room.

The stratum key is the joined values of key_columns. A row missing any key column belongs to no stratum and is not sampled — silently folding it into a partial key would merge unrelated rows into one stratum.

pub fn strata_seen(&self) -> usize

Number of distinct strata observed so far.

Trait Implementations

impl Debug for SamplingState

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

Formats the value using the given formatter.

impl Default for SamplingState

fn default() -> SamplingState

Returns the “default value” for a type.