dataprof_core/sampling/
strategies.rs

1/// How rows are selected for profiling.
2///
3/// Strategies divide into two families, which differ in cost.
4/// [`Systematic`](Self::Systematic) decides each row as it arrives and adds no
5/// memory. [`Random`](Self::Random) and [`Reservoir`](Self::Reservoir) cannot
6/// know the final sample until the source ends, so they hold `size` rows in
7/// memory and the profile is computed from that buffer.
8///
9/// Every strategy is applied by `RowSampler`.
10#[derive(Debug, Clone)]
11pub enum SamplingStrategy {
12    /// No sampling - analyze all data
13    None,
14
15    /// A uniform random sample of exactly `size` rows (or every row, when the
16    /// source is shorter).
17    ///
18    /// Over a source of unknown length this is reservoir sampling, so it holds
19    /// `size` rows in memory and is equivalent to
20    /// [`Reservoir`](Self::Reservoir); both names are kept because both are
21    /// familiar.
22    Random { size: usize },
23
24    /// A uniform random sample of exactly `size` rows, selected with Algorithm
25    /// R over a single pass.
26    ///
27    /// Holds `size` rows in memory: membership is not final until the source
28    /// ends, and statistics folded in earlier could not be retracted.
29    Reservoir { size: usize },
30
31    /// Every `interval`-th row, starting at the first.
32    Systematic { interval: usize },
33}
34
35impl SamplingStrategy {
36    /// Get description of the sampling strategy
37    pub fn description(&self) -> String {
38        match self {
39            SamplingStrategy::None => "Full dataset analysis".to_string(),
40            SamplingStrategy::Random { size } => format!("Random sampling ({} records)", size),
41            SamplingStrategy::Reservoir { size } => {
42                format!("Reservoir sampling ({} records)", size)
43            }
44            SamplingStrategy::Systematic { interval } => {
45                format!("Systematic (every {}th record)", interval)
46            }
47        }
48    }
49}
dataprof_core/sampling/strategies.rs

dataprof_core/sampling/
strategies.rs
