sk

core/store/src/trie/mem/updating.rs

@@ -44,13 +44,25 @@ pub enum UpdatedMemTrieNode {
     },
 }
 
+/// Keeps values and internal nodes accessed on updating memtrie.
 pub(crate) struct TrieAccesses {
+    /// Hashes and encoded trie nodes.
     pub nodes: HashMap<CryptoHash, Arc<[u8]>>,
+    /// Hashes of accessed values - because values themselves are not
+    /// necessarily present in memtrie.
     pub values: HashSet<CryptoHash>,
 }
 
+/// Tracks intermediate trie changes, final version of which is to be committed
+/// to disk after finishing trie update.
 struct TrieChangesTracker {
+    /// Changes of reference count on disk for each impacted node.
     refcount_changes: TrieRefcountDeltaMap,
+    /// All observed values and internal nodes.
+    /// Needed to prepare recorded storage.
+    /// Note that negative `refcount_changes` does not fully cover it, as node
+    /// or value of the same hash can be removed and inserted for the same
+    /// update in different parts of trie!
     accesses: TrieAccesses,
 }
 
@@ -64,7 +76,8 @@ pub struct MemTrieUpdate<'a> {
     /// (1) temporarily we take out the node from the slot to process it and put it back
     /// later; or (2) the node is deleted afterwards.
     pub updated_nodes: Vec<Option<UpdatedMemTrieNode>>,
-    /// Refcount changes to on-disk trie nodes.
+    /// Tracks trie changes necessary to make on-disk updates and recorded
+    /// storage.
     tracked_trie_changes: Option<TrieChangesTracker>,
 }
 

core/store/src/trie/mod.rs

@@ -1500,6 +1500,8 @@ impl Trie {
                 }
                 let (trie_changes, trie_accesses) = trie_update.to_trie_changes();
 
+                // Sanity check for tests: all modified trie items must be
+                // present in ever accessed trie items.
                 #[cfg(test)]
                 {
                     for t in trie_changes.deletions.iter() {
@@ -1513,6 +1515,9 @@ impl Trie {
                     }
                 }
 
+                // Retroactively record all accessed trie items to account for
+                // key-value pairs which were only written but never read, thus
+                // not recorded before.
                 if let Some(recorder) = &self.recorder {
                     for (node_hash, serialized_node) in trie_accesses.nodes {
                         recorder.borrow_mut().record(&node_hash, serialized_node);

core/store/src/trie/trie_recording.rs

@@ -239,7 +239,6 @@ mod trie_recording_tests {
                     data_in_trie.get(key).map(|value| ValueRef::new(&value))
                 );
             }
-            trie.accounting_cache.borrow_mut().set_enabled(false);
             assert_eq!(trie.get_trie_nodes_count(), baseline_trie_nodes_count);
             trie.update(updates.iter().cloned()).unwrap();