feat(graph):优化Nebula图数据库查询性能

Author: Nyakult

src/memos/graph_dbs/nebular.py

@@ -1131,7 +1131,7 @@ def get_grouped_counts(
             group_by_fields.append(alias)
         # Full GQL query construction
         gql = f"""
-            MATCH (n)
+            MATCH (n /*+ INDEX(idx_memory_user_name) */)
             {where_clause}
             RETURN {", ".join(return_fields)}, COUNT(n) AS count
             GROUP BY {", ".join(group_by_fields)}