don't snapshot empty db files (#730)

Author: Horusiath

bottomless/src/replicator.rs

@@ -1095,13 +1095,17 @@ impl Replicator {
                 if let Ok(page_size) = Self::read_page_size(&mut db).await {
                     self.set_page_size(page_size)?;
                 }
-                // if database file exists always treat it as new and more up to date, skipping the
-                // restoration process and calling for a new generation to be made
-                return Ok(Some(RestoreAction::SnapshotMainDbFile));
+                Self::read_change_counter(&mut db).await.unwrap_or([0u8; 4])
             }
             Err(_) => [0u8; 4],
         };
 
+        if local_counter != [0u8; 4] {
+            // if a non-empty database file exists always treat it as new and more up to date,
+            // skipping the restoration process and calling for a new generation to be made
+            return Ok(Some(RestoreAction::SnapshotMainDbFile));
+        }
+
         let remote_counter = self.get_remote_change_counter(&generation).await?;
         tracing::debug!("Counters: l={:?}, r={:?}", local_counter, remote_counter);