minor fix

Committed-by: xiaolei.zl from Dev container

Author: zhanglei1949

flex/engines/http_server/graph_db_service.cc

@@ -100,7 +100,12 @@ void openGraph(const gs::GraphId& graph_id,
                            service_config.shard_num);
   config.memory_level = service_config.memory_level;
   config.wal_uri = service_config.wal_uri;
-  LOG(FATAL) << "Fail to load graph from data directory: " << data_dir;
+  if (config.memory_level >= 2) {
+    config.enable_auto_compaction = true;
+  }
+  if (!db.Open(config).ok()) {
+    LOG(FATAL) << "Fail to load graph from data directory: " << data_dir;
+  }
   LOG(INFO) << "Successfully init graph db for graph: " << graph_id;
 }