iridium-db 0.2.0

A high-performance vector-graph hybrid storage and indexing engine
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70

#[derive(Debug, Clone, Copy, PartialEq)]
pub struct LevelBpk {
    pub level: u32,
    pub bits_per_key: f32,
}

#[derive(Debug, Clone)]
pub struct BloomTuningResult {
    pub levels: Vec<LevelBpk>,
}

pub struct BloomTuningPolicy {
    pub base_bpk: f32,
    pub min_bpk: f32,
    pub max_bpk: f32,
}

impl BloomTuningPolicy {
    pub fn new(base_bpk: f32, min_bpk: f32, max_bpk: f32) -> Self {
        Self {
            base_bpk,
            min_bpk,
            max_bpk,
        }
    }

    pub fn tune(&self, level_count: u32) -> BloomTuningResult {
        let mut levels = Vec::new();
        for level in 0..level_count {
            let decay = 1.0 / (1.0 + level as f32 * 0.5);
            let mut bpk = self.base_bpk * decay;
            if bpk < self.min_bpk {
                bpk = self.min_bpk;
            }
            if bpk > self.max_bpk {
                bpk = self.max_bpk;
            }
            levels.push(LevelBpk {
                level,
                bits_per_key: bpk,
            });
        }
        BloomTuningResult { levels }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn bloom_tuning_monotonic_decay() {
        let policy = BloomTuningPolicy::new(16.0, 4.0, 16.0);
        let result = policy.tune(4);
        assert_eq!(result.levels.len(), 4);
        assert!(result.levels[0].bits_per_key >= result.levels[1].bits_per_key);
        assert!(result.levels[1].bits_per_key >= result.levels[2].bits_per_key);
        assert!(result.levels[2].bits_per_key >= result.levels[3].bits_per_key);
    }

    #[test]
    fn bloom_tuning_respects_bounds() {
        let policy = BloomTuningPolicy::new(12.0, 6.0, 10.0);
        let result = policy.tune(6);
        for level in result.levels {
            assert!(level.bits_per_key >= 6.0);
            assert!(level.bits_per_key <= 10.0);
        }
    }
}