refactor(metrics): add dedicated range tombstone block counters

src/metrics.rs

@@ -34,6 +34,12 @@ pub struct Metrics {
     /// Number of blocks that were read from block cache
     pub(crate) data_block_load_cached: AtomicUsize,
 
+    /// Number of range tombstone blocks that were actually read from disk
+    pub(crate) range_tombstone_block_load_io: AtomicUsize,
+
+    /// Number of range tombstone blocks that were read from block cache
+    pub(crate) range_tombstone_block_load_cached: AtomicUsize,
+
     /// Number of filter queries that were performed
     pub(crate) filter_queries: AtomicUsize,
 
@@ -48,6 +54,9 @@ pub struct Metrics {
 
     /// Number of filter block bytes that were requested from OS or disk
     pub(crate) filter_block_io_requested: AtomicU64,
+
+    /// Number of range tombstone block bytes that were requested from OS or disk
+    pub(crate) range_tombstone_block_io_requested: AtomicU64,
 }
 
 #[expect(
@@ -82,11 +91,17 @@ impl Metrics {
         self.filter_block_io_requested.load(Relaxed)
     }
 
+    /// Number of I/O range tombstone block bytes transferred from disk or OS page cache.
+    pub fn range_tombstone_block_io(&self) -> u64 {
+        self.range_tombstone_block_io_requested.load(Relaxed)
+    }
+
     /// Number of I/O block bytes transferred from disk or OS page cache.
     pub fn block_io(&self) -> u64 {
         self.data_block_io_requested.load(Relaxed)
             + self.index_block_io_requested.load(Relaxed)
             + self.filter_block_io_requested.load(Relaxed)
+            + self.range_tombstone_block_io_requested.load(Relaxed)
     }
 
     /// Number of data blocks that were accessed.
@@ -104,11 +119,18 @@ impl Metrics {
         self.filter_block_load_cached.load(Relaxed) + self.filter_block_load_io.load(Relaxed)
     }
 
+    /// Number of range tombstone blocks that were accessed.
+    pub fn range_tombstone_block_load_count(&self) -> usize {
+        self.range_tombstone_block_load_cached.load(Relaxed)
+            + self.range_tombstone_block_load_io.load(Relaxed)
+    }
+
     /// Number of blocks that were loaded from disk or OS page cache.
     pub fn block_load_io_count(&self) -> usize {
         self.data_block_load_io.load(Relaxed)
             + self.index_block_load_io.load(Relaxed)
             + self.filter_block_load_io.load(Relaxed)
+            + self.range_tombstone_block_load_io.load(Relaxed)
     }
 
     /// Number of data blocks that were loaded from disk or OS page cache.
@@ -126,11 +148,17 @@ impl Metrics {
         self.filter_block_load_cached.load(Relaxed)
     }
 
+    /// Number of range tombstone blocks that were loaded from block cache.
+    pub fn range_tombstone_block_load_cached_count(&self) -> usize {
+        self.range_tombstone_block_load_cached.load(Relaxed)
+    }
+
     /// Number of blocks that were loaded from disk or OS page cache.
     pub fn block_load_cached_count(&self) -> usize {
         self.data_block_load_cached.load(Relaxed)
             + self.index_block_load_cached.load(Relaxed)
             + self.filter_block_load_cached.load(Relaxed)
+            + self.range_tombstone_block_load_cached.load(Relaxed)
     }
 
     /// Number of blocks that were accessed.
@@ -174,6 +202,18 @@ impl Metrics {
         }
     }
 
+    /// Range tombstone block cache efficiency in percent (0.0 - 1.0).
+    pub fn range_tombstone_block_cache_hit_rate(&self) -> f64 {
+        let queries = self.range_tombstone_block_load_count() as f64;
+        let hits = self.range_tombstone_block_load_cached_count() as f64;
+
+        if queries == 0.0 {
+            1.0
+        } else {
+            hits / queries
+        }
+    }
+
     /// Block cache efficiency in percent (0.0 - 1.0).
     pub fn block_cache_hit_rate(&self) -> f64 {
         let queries = self.block_loads() as f64;

src/table/util.rs

@@ -60,9 +60,12 @@ pub fn load_block(
             BlockType::Index => {
                 metrics.index_block_load_cached.fetch_add(1, Relaxed);
             }
-            // TODO(#34): RangeTombstone counted under data_block metrics — add
-            // dedicated range_tombstone_block_load_cached/miss counters
-            BlockType::Data | BlockType::Meta | BlockType::RangeTombstone => {
+            BlockType::RangeTombstone => {
+                metrics
+                    .range_tombstone_block_load_cached
+                    .fetch_add(1, Relaxed);
+            }
+            BlockType::Data | BlockType::Meta => {
                 metrics.data_block_load_cached.fetch_add(1, Relaxed);
             }
         }
@@ -109,8 +112,14 @@ pub fn load_block(
                 .index_block_io_requested
                 .fetch_add(handle.size().into(), Relaxed);
         }
-        // TODO(#34): same as above — RangeTombstone uses data_block IO counters
-        BlockType::Data | BlockType::Meta | BlockType::RangeTombstone => {
+        BlockType::RangeTombstone => {
+            metrics.range_tombstone_block_load_io.fetch_add(1, Relaxed);
+
+            metrics
+                .range_tombstone_block_io_requested
+                .fetch_add(handle.size().into(), Relaxed);
+        }
+        BlockType::Data | BlockType::Meta => {
             metrics.data_block_load_io.fetch_add(1, Relaxed);
 
             metrics