Merge pull request #3311 from Pana/chore/smallOp

op: only read from storage if cache entry is not occupied

Author: Pana

crates/dbs/statedb/src/lib.rs

@@ -83,24 +83,20 @@ mod impls {
             &self, key: StorageKeyWithSpace,
         ) -> Result<Option<Arc<[u8]>>> {
             let key_bytes = key.to_key_bytes();
-            let mut r;
+            let r;
             let accessed_entries_read_guard = self.accessed_entries.read();
             if let Some(v) = accessed_entries_read_guard.get(&key_bytes) {
                 r = v.current_value.clone();
             } else {
                 drop(accessed_entries_read_guard);
-                r = self.storage.get(key)?.map(Into::into);
                 let mut accessed_entries = self.accessed_entries.write();
                 let entry = accessed_entries.entry(key_bytes);
-                let was_vacant = if let Occupied(o) = &entry {
+                if let Occupied(o) = &entry {
                     r = o.get().current_value.clone();
-                    false
                 } else {
-                    true
-                };
-                if was_vacant {
+                    r = self.storage.get(key)?.map(Into::into);
                     entry.or_insert(EntryValue::new(r.clone()));
-                }
+                };
             };
             trace!("get_raw key={:?}, value={:?}", key, r);
             Ok(r)