Function select_segments_for_compaction

nodedb/src/storage/compaction.rs:102–128

Select segments for compaction based on the configuration. Returns segments to compact, sorted by min_lsn (oldest first). Selects segments that: 1. Are too small (below target size) 2. Have high tombstone ratios 3. Are adjacent in LSN space (can be merged cleanly)

(
    segments: &[SegmentMeta],
    config: &CompactionConfig,
)

/// 2. Have high tombstone ratios
/// 3. Are adjacent in LSN space (can be merged cleanly)
pub fn select_segments_for_compaction(
    segments: &[SegmentMeta],
    config: &CompactionConfig,
) -> Vec<usize> {
    if segments.len() < config.min_segments_to_compact {
        return Vec::new();
    }

    let mut candidates: Vec<(usize, &SegmentMeta)> = segments
        .iter()
        .enumerate()
        .filter(|(_, s)| {
            s.size_bytes < config.target_segment_bytes as u64
                || s.needs_compaction(config.tombstone_ratio_threshold)
        })
        .collect();

    // Sort by min_lsn (oldest first) for monotonic ordering.
    candidates.sort_by_key(|(_, s)| s.min_lsn);

    // Take up to max_segments_per_pass.
    candidates
        .iter()
        .take(config.max_segments_per_pass)
        .map(|(i, _)| *i)
        .collect()
}

/// Plan a compaction: compute the expected output segment metadata.
///