perf(db): flatten HashedPostState before persisting

crates/storage/provider/src/providers/database/provider.rs

@@ -630,27 +630,27 @@ impl<TX: DbTx + DbTxMut + 'static, N: NodeTypesForProvider> DatabaseProvider<TX,
                         },
                     )?;
                     timings.write_state += start.elapsed();
-
-                    let trie_data = block.trie_data();
-
-                    // insert hashes and intermediate merkle nodes
-                    let start = Instant::now();
-                    self.write_hashed_state(&trie_data.hashed_state)?;
-                    timings.write_hashed_state += start.elapsed();
                 }
             }
 
-            // Write all trie updates in a single batch.
+            // Write all hashed state and trie updates in single batches.
             // This reduces cursor open/close overhead from N calls to 1.
             if save_mode.with_state() {
+                // Blocks are oldest-to-newest, merge_batch expects newest-to-oldest.
                 let start = Instant::now();
+                let merged_hashed_state = HashedPostStateSorted::merge_batch(
+                    blocks.iter().rev().map(|b| b.trie_data().hashed_state),
+                );
+                if !merged_hashed_state.is_empty() {
+                    self.write_hashed_state(&merged_hashed_state)?;
+                }
+                timings.write_hashed_state += start.elapsed();
 
-                // Blocks are oldest-to-newest, merge_batch expects newest-to-oldest.
-                let merged =
+                let start = Instant::now();
+                let merged_trie =
                     TrieUpdatesSorted::merge_batch(blocks.iter().rev().map(|b| b.trie_updates()));
-
-                if !merged.is_empty() {
-                    self.write_trie_updates_sorted(&merged)?;
+                if !merged_trie.is_empty() {
+                    self.write_trie_updates_sorted(&merged_trie)?;
                 }
                 timings.write_trie_updates += start.elapsed();
             }