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use super::merge_policy::{MergeCandidate, MergePolicy};
use crate::core::SegmentMeta;
use std::cmp;
use std::f64;
const DEFAULT_LEVEL_LOG_SIZE: f64 = 0.75;
const DEFAULT_MIN_LAYER_SIZE: u32 = 10_000;
const DEFAULT_MIN_MERGE_SIZE: usize = 8;
#[derive(Debug, Clone)]
pub struct LogMergePolicy {
min_merge_size: usize,
min_layer_size: u32,
level_log_size: f64,
}
impl LogMergePolicy {
fn clip_min_size(&self, size: u32) -> u32 {
cmp::max(self.min_layer_size, size)
}
pub fn set_min_merge_size(&mut self, min_merge_size: usize) {
self.min_merge_size = min_merge_size;
}
pub fn set_min_layer_size(&mut self, min_layer_size: u32) {
self.min_layer_size = min_layer_size;
}
pub fn set_level_log_size(&mut self, level_log_size: f64) {
self.level_log_size = level_log_size;
}
}
impl MergePolicy for LogMergePolicy {
fn compute_merge_candidates(&self, segments: &[SegmentMeta]) -> Vec<MergeCandidate> {
if segments.is_empty() {
return Vec::new();
}
let mut size_sorted_tuples = segments
.iter()
.map(SegmentMeta::num_docs)
.enumerate()
.collect::<Vec<(usize, u32)>>();
size_sorted_tuples.sort_by(|x, y| y.1.cmp(&(x.1)));
let size_sorted_log_tuples: Vec<_> = size_sorted_tuples
.into_iter()
.map(|(ind, num_docs)| (ind, f64::from(self.clip_min_size(num_docs)).log2()))
.collect();
let (first_ind, first_score) = size_sorted_log_tuples[0];
let mut current_max_log_size = first_score;
let mut levels = vec![vec![first_ind]];
for &(ind, score) in (&size_sorted_log_tuples).iter().skip(1) {
if score < (current_max_log_size - self.level_log_size) {
current_max_log_size = score;
levels.push(Vec::new());
}
levels.last_mut().unwrap().push(ind);
}
levels
.iter()
.filter(|level| level.len() >= self.min_merge_size)
.map(|ind_vec| MergeCandidate(ind_vec.iter().map(|&ind| segments[ind].id()).collect()))
.collect()
}
}
impl Default for LogMergePolicy {
fn default() -> LogMergePolicy {
LogMergePolicy {
min_merge_size: DEFAULT_MIN_MERGE_SIZE,
min_layer_size: DEFAULT_MIN_LAYER_SIZE,
level_log_size: DEFAULT_LEVEL_LOG_SIZE,
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::core::{SegmentId, SegmentMeta, SegmentMetaInventory};
use crate::indexer::merge_policy::MergePolicy;
use once_cell::sync::Lazy;
static INVENTORY: Lazy<SegmentMetaInventory> = Lazy::new(SegmentMetaInventory::default);
fn test_merge_policy() -> LogMergePolicy {
let mut log_merge_policy = LogMergePolicy::default();
log_merge_policy.set_min_merge_size(3);
log_merge_policy.set_min_layer_size(2);
log_merge_policy
}
#[test]
fn test_log_merge_policy_empty() {
let y = Vec::new();
let result_list = test_merge_policy().compute_merge_candidates(&y);
assert!(result_list.is_empty());
}
fn create_random_segment_meta(num_docs: u32) -> SegmentMeta {
INVENTORY.new_segment_meta(SegmentId::generate_random(), num_docs)
}
#[test]
fn test_log_merge_policy_pair() {
let test_input = vec![
create_random_segment_meta(10),
create_random_segment_meta(10),
create_random_segment_meta(10),
];
let result_list = test_merge_policy().compute_merge_candidates(&test_input);
assert_eq!(result_list.len(), 1);
}
#[test]
fn test_log_merge_policy_levels() {
let test_input = vec![
create_random_segment_meta(10),
create_random_segment_meta(10),
create_random_segment_meta(10),
create_random_segment_meta(1000),
create_random_segment_meta(1000),
create_random_segment_meta(1000),
create_random_segment_meta(10000),
create_random_segment_meta(10000),
create_random_segment_meta(10),
create_random_segment_meta(10),
create_random_segment_meta(10),
];
let result_list = test_merge_policy().compute_merge_candidates(&test_input);
assert_eq!(result_list.len(), 2);
}
#[test]
fn test_log_merge_policy_within_levels() {
let test_input = vec![
create_random_segment_meta(10),
create_random_segment_meta(11),
create_random_segment_meta(12),
create_random_segment_meta(800),
create_random_segment_meta(1000),
create_random_segment_meta(1000),
];
let result_list = test_merge_policy().compute_merge_candidates(&test_input);
assert_eq!(result_list.len(), 2);
}
#[test]
fn test_log_merge_policy_small_segments() {
let test_input = vec![
create_random_segment_meta(1),
create_random_segment_meta(1),
create_random_segment_meta(1),
create_random_segment_meta(2),
create_random_segment_meta(2),
create_random_segment_meta(2),
];
let result_list = test_merge_policy().compute_merge_candidates(&test_input);
assert_eq!(result_list.len(), 1);
}
}