diff --git a/src/memos/graph_dbs/polardb.py b/src/memos/graph_dbs/polardb.py
index d3dc1b4f9..7db840082 100644
--- a/src/memos/graph_dbs/polardb.py
+++ b/src/memos/graph_dbs/polardb.py
@@ -151,7 +151,7 @@ def __init__(self, config: PolarDBGraphDBConfig):
         # Create connection pool
         self.connection_pool = psycopg2.pool.ThreadedConnectionPool(
             minconn=5,
-            maxconn=2000,
+            maxconn=100,
             host=host,
             port=port,
             user=user,
@@ -1338,6 +1338,7 @@ def get_subgraph(
                 "edges": [...]
             }
         """
+        logger.info(f"[get_subgraph] center_id: {center_id}")
         if not 1 <= depth <= 5:
             raise ValueError("depth must be 1-5")
 
@@ -1375,6 +1376,7 @@ def get_subgraph(
                 $$ ) as (centers agtype, neighbors agtype, rels agtype);
             """
         conn = self._get_connection()
+        logger.info(f"[get_subgraph] Query: {query}")
         try:
             with conn.cursor() as cursor:
                 cursor.execute(query)
@@ -1746,6 +1748,7 @@ def search_by_embedding(
 
         # Build filter conditions using common method
         filter_conditions = self._build_filter_conditions_sql(filter)
+        logger.info(f"[search_by_embedding] filter_conditions: {filter_conditions}")
         where_clauses.extend(filter_conditions)
 
         where_clause = f"WHERE {' AND '.join(where_clauses)}" if where_clauses else ""
@@ -1918,7 +1921,7 @@ def get_by_metadata(
             knowledgebase_ids=knowledgebase_ids,
             default_user_name=self._get_config_value("user_name"),
         )
-        print(f"[111get_by_metadata] user_name_conditions: {user_name_conditions}")
+        logger.info(f"[get_by_metadata] user_name_conditions: {user_name_conditions}")
 
         # Add user_name WHERE clause
         if user_name_conditions:
@@ -1929,6 +1932,7 @@ def get_by_metadata(
 
         # Build filter conditions using common method
         filter_where_clause = self._build_filter_conditions_cypher(filter)
+        logger.info(f"[get_by_metadata] filter_where_clause: {filter_where_clause}")
 
         where_str = " AND ".join(where_conditions) + filter_where_clause
 
@@ -2393,6 +2397,7 @@ def get_all_memory_items(
 
         # Build filter conditions using common method
         filter_where_clause = self._build_filter_conditions_cypher(filter)
+        logger.info(f"[get_all_memory_items] filter_where_clause: {filter_where_clause}")
 
         # Use cypher query to retrieve memory items
         if include_embedding:
@@ -2426,6 +2431,7 @@ def get_all_memory_items(
             nodes = []
             node_ids = set()
             conn = self._get_connection()
+            logger.info(f"[get_all_memory_items] cypher_query: {cypher_query}")
             try:
                 with conn.cursor() as cursor:
                     cursor.execute(cypher_query)
@@ -3456,7 +3462,11 @@ def _convert_graph_edges(self, core_node: dict) -> dict:
         id_map = {}
         core_node = data.get("core_node", {})
         if not core_node:
-            return core_node
+            return {
+                "core_node": None,
+                "neighbors": data.get("neighbors", []),
+                "edges": data.get("edges", []),
+            }
         core_meta = core_node.get("metadata", {})
         if "graph_id" in core_meta and "id" in core_node:
             id_map[core_meta["graph_id"]] = core_node["id"]
@@ -3507,7 +3517,6 @@ def _build_user_name_and_kb_ids_conditions_cypher(
         """
         user_name_conditions = []
         effective_user_name = user_name if user_name else default_user_name
-        print(f"[delete_node_by_prams] effective_user_name: {effective_user_name}")
 
         if effective_user_name:
             escaped_user_name = effective_user_name.replace("'", "''")
diff --git a/src/memos/memories/textual/tree.py b/src/memos/memories/textual/tree.py
index c53c13618..25e6276d9 100644
--- a/src/memos/memories/textual/tree.py
+++ b/src/memos/memories/textual/tree.py
@@ -262,15 +262,16 @@ def get_relevant_subgraph(
             )
 
             if subgraph is None or not subgraph["core_node"]:
-                logger.info(f"Skipping node {core_id} (inactive or not found).")
-                continue
+                node = self.graph_store.get_node(core_id, user_name=user_name)
+                subgraph["neighbors"] = [node]
 
             core_node = subgraph["core_node"]
             neighbors = subgraph["neighbors"]
             edges = subgraph["edges"]
 
             # Collect nodes
-            all_nodes[core_node["id"]] = core_node
+            if core_node:
+                all_nodes[core_node["id"]] = core_node
             for n in neighbors:
                 all_nodes[n["id"]] = n
 
@@ -339,28 +340,6 @@ def delete_all(self) -> None:
             logger.error(f"An error occurred while deleting all memories: {e}")
             raise
 
-    def delete_by_filter(
-        self,
-        writable_cube_ids: list[str],
-        memory_ids: list[str] | None = None,
-        file_ids: list[str] | None = None,
-        filter: dict | None = None,
-    ) -> int:
-        """Delete memories by filter.
-        Returns:
-            int: Number of nodes deleted.
-        """
-        try:
-            return self.graph_store.delete_node_by_prams(
-                writable_cube_ids=writable_cube_ids,
-                memory_ids=memory_ids,
-                file_ids=file_ids,
-                filter=filter,
-            )
-        except Exception as e:
-            logger.error(f"An error occurred while deleting memories by filter: {e}")
-            raise
-
     def load(self, dir: str) -> None:
         try:
             memory_file = os.path.join(dir, self.config.memory_filename)