finish leveled compaction

Signed-off-by: Alex Chi <iskyzh@gmail.com>

mini-lsm/src/compact/leveled.rs

@@ -1,18 +1,150 @@
+use std::collections::HashSet;
+
 use crate::lsm_storage::LsmStorageInner;
 
 pub struct LeveledCompactionTask {
     // if upper_level is `None`, then it is L0 compaction
-    upper_level: Option<usize>,
-    upper_level_sst_ids: Vec<usize>,
-    lower_level: usize,
-    lower_level_sst_ids: Vec<usize>,
+    pub upper_level: Option<usize>,
+    pub upper_level_sst_ids: Vec<usize>,
+    pub lower_level: usize,
+    pub lower_level_sst_ids: Vec<usize>,
 }
 
-pub struct LeveledCompactionController {}
+pub struct LeveledCompactionOptions {
+    pub level_size_multiplier: usize,
+    pub level0_file_num_compaction_trigger: usize,
+    pub max_levels: usize,
+    pub base_level_size_mb: usize,
+}
+
+pub struct LeveledCompactionController {
+    options: LeveledCompactionOptions,
+}
 
 impl LeveledCompactionController {
-    pub fn generate_compaction_task(&self, snapshot: &LsmStorageInner) -> LeveledCompactionTask {
-        unimplemented!()
+    pub fn new(options: LeveledCompactionOptions) -> Self {
+        Self { options }
+    }
+
+    fn find_overlapping_ssts(
+        &self,
+        snapshot: &LsmStorageInner,
+        sst_ids: &[usize],
+        in_level: usize,
+    ) -> Vec<usize> {
+        let begin_key = sst_ids
+            .iter()
+            .map(|id| snapshot.sstables[id].first_key())
+            .min()
+            .cloned()
+            .unwrap();
+        let end_key = sst_ids
+            .iter()
+            .map(|id| snapshot.sstables[id].last_key())
+            .max()
+            .cloned()
+            .unwrap();
+        let mut overlap_ssts = Vec::new();
+        for sst_id in &snapshot.levels[in_level - 1].1 {
+            let sst = &snapshot.sstables[sst_id];
+            let first_key = sst.first_key();
+            let last_key = sst.last_key();
+            if !(last_key < &begin_key || first_key > &end_key) {
+                overlap_ssts.push(*sst_id);
+            }
+        }
+        overlap_ssts
+    }
+
+    pub fn generate_compaction_task(
+        &self,
+        snapshot: &LsmStorageInner,
+    ) -> Option<LeveledCompactionTask> {
+        // step 1: compute target level size
+        let mut target_level_size = (0..self.options.max_levels).map(|_| 0).collect::<Vec<_>>(); // exclude level 0
+        let mut real_level_size = Vec::with_capacity(self.options.max_levels);
+        let mut base_level = self.options.max_levels;
+        for i in 0..self.options.max_levels {
+            real_level_size.push(
+                snapshot.levels[i]
+                    .1
+                    .iter()
+                    .map(|x| snapshot.sstables.get(x).unwrap().table_size())
+                    .sum::<u64>() as usize,
+            );
+        }
+        let base_level_size_bytes = self.options.base_level_size_mb as usize * 1024 * 1024;
+
+        // select base level and compute target level size
+        target_level_size[self.options.max_levels - 1] =
+            real_level_size[self.options.max_levels - 1].max(base_level_size_bytes);
+        for i in (0..(self.options.max_levels - 1)).rev() {
+            let next_level_size = target_level_size[i + 1];
+            let this_level_size = next_level_size / self.options.level_size_multiplier;
+            if next_level_size > base_level_size_bytes {
+                target_level_size[i] = this_level_size;
+            }
+            if target_level_size[i] > 0 {
+                base_level = i + 1;
+            }
+        }
+
+        println!(
+            "target level sizes: {:?}, real level sizes: {:?}, base_level: {}",
+            target_level_size
+                .iter()
+                .map(|x| format!("{}MB", x / 1024 / 1024))
+                .collect::<Vec<_>>(),
+            real_level_size
+                .iter()
+                .map(|x| format!("{}MB", x / 1024 / 1024))
+                .collect::<Vec<_>>(),
+            base_level,
+        );
+
+        // Flush L0 SST is the top priority
+        if snapshot.l0_sstables.len() >= self.options.level0_file_num_compaction_trigger {
+            println!("flush L0 SST to base level {}", base_level);
+            return Some(LeveledCompactionTask {
+                upper_level: None,
+                upper_level_sst_ids: snapshot.l0_sstables.clone(),
+                lower_level: base_level,
+                lower_level_sst_ids: self.find_overlapping_ssts(
+                    snapshot,
+                    &snapshot.l0_sstables,
+                    base_level,
+                ),
+            });
+        }
+
+        let mut priorities = Vec::with_capacity(self.options.max_levels);
+        for level in 0..self.options.max_levels {
+            let prio = real_level_size[level] as f64 / target_level_size[level] as f64;
+            if prio > 1.0 {
+                priorities.push((prio, level + 1));
+            }
+        }
+        priorities.sort_by(|a, b| a.partial_cmp(b).unwrap().reverse());
+        let priority = priorities.first();
+        if let Some((_, level)) = priority {
+            let level = *level;
+            let selected_sst = snapshot.levels[level - 1].1.iter().min().copied().unwrap(); // select the oldest sst to compact
+            println!(
+                "compaction triggered by priority: {level} out of {:?}, select {selected_sst} for compaction",
+                priorities
+            );
+            return Some(LeveledCompactionTask {
+                upper_level: Some(level),
+                upper_level_sst_ids: vec![selected_sst],
+                lower_level: level + 1,
+                lower_level_sst_ids: self.find_overlapping_ssts(
+                    snapshot,
+                    &[selected_sst],
+                    level + 1,
+                ),
+            });
+        }
+        None
     }
 
     pub fn apply_compaction_result(
@@ -21,6 +153,71 @@ impl LeveledCompactionController {
         task: &LeveledCompactionTask,
         output: &[usize],
     ) -> (LsmStorageInner, Vec<usize>) {
-        unimplemented!()
+        let mut snapshot = snapshot.clone();
+        let mut files_to_remove = Vec::new();
+        let mut upper_level_sst_ids_set = task
+            .upper_level_sst_ids
+            .iter()
+            .copied()
+            .collect::<HashSet<_>>();
+        let mut lower_level_sst_ids_set = task
+            .lower_level_sst_ids
+            .iter()
+            .copied()
+            .collect::<HashSet<_>>();
+        if let Some(upper_level) = task.upper_level {
+            let new_upper_level_ssts =
+                snapshot.levels[upper_level - 1]
+                    .1
+                    .iter()
+                    .filter_map(|x| {
+                        if upper_level_sst_ids_set.remove(x) {
+                            return None;
+                        }
+                        Some(*x)
+                    })
+                    .collect::<Vec<_>>();
+            assert!(upper_level_sst_ids_set.is_empty());
+            snapshot.levels[upper_level - 1].1 = new_upper_level_ssts;
+        } else {
+            let new_l0_ssts = snapshot
+                .l0_sstables
+                .iter()
+                .filter_map(|x| {
+                    if upper_level_sst_ids_set.remove(x) {
+                        return None;
+                    }
+                    Some(*x)
+                })
+                .collect::<Vec<_>>();
+            assert!(upper_level_sst_ids_set.is_empty());
+            snapshot.l0_sstables = new_l0_ssts;
+        }
+
+        files_to_remove.extend(&task.upper_level_sst_ids);
+        files_to_remove.extend(&task.lower_level_sst_ids);
+
+        let mut new_lower_level_ssts = snapshot.levels[task.lower_level - 1]
+            .1
+            .iter()
+            .filter_map(|x| {
+                if lower_level_sst_ids_set.remove(x) {
+                    return None;
+                }
+                Some(*x)
+            })
+            .collect::<Vec<_>>();
+        assert!(lower_level_sst_ids_set.is_empty());
+        new_lower_level_ssts.extend(output);
+        new_lower_level_ssts.sort_by(|x, y| {
+            snapshot
+                .sstables
+                .get(x)
+                .unwrap()
+                .first_key()
+                .cmp(snapshot.sstables.get(y).unwrap().first_key())
+        });
+        snapshot.levels[task.lower_level - 1].1 = new_lower_level_ssts;
+        (snapshot, files_to_remove)
     }
 }

mini-lsm/src/compact/simple_leveled.rs

@@ -1,5 +1,3 @@
-use std::collections::HashMap;
-
 use crate::lsm_storage::LsmStorageInner;
 
 pub struct SimpleLeveledCompactionOptions {

mini-lsm/src/compact/tiered.rs

@@ -73,7 +73,7 @@ impl TieredCompactionController {
         }
         // trying to reduce sorted runs without respecting size ratio
         let num_tiers_to_take =
-            snapshot.levels.len() - self.options.level0_file_num_compaction_trigger + 1;
+            snapshot.levels.len() - self.options.level0_file_num_compaction_trigger + 2;
         println!("compaction triggered by reducing sorted runs");
         return Some(TieredCompactionTask {
             tiers: snapshot