diff --git a/lightrag/kg/postgres_impl.py b/lightrag/kg/postgres_impl.py
index 3c88a05b..044bf4c1 100644
--- a/lightrag/kg/postgres_impl.py
+++ b/lightrag/kg/postgres_impl.py
@@ -88,7 +88,16 @@ class PostgreSQLDB:
 
     async def check_graph_requirement(self, graph_name: str):
         async with self.pool.acquire() as connection:  # type: ignore
-            await self._prerequisite(connection, graph_name)  # type: ignore
+            try:
+                await connection.execute(
+                    'SET search_path = ag_catalog, "$user", public'
+                )  # type: ignore
+                await connection.execute(f"select create_graph('{graph_name}')")  # type: ignore
+            except (
+                asyncpg.exceptions.InvalidSchemaNameError,
+                asyncpg.exceptions.UniqueViolationError,
+            ):
+                pass
 
     async def check_tables(self):
         for k, v in TABLES.items():
@@ -106,8 +115,6 @@ class PostgreSQLDB:
                     )
                     raise e
 
-        logger.info("Finished checking all tables in PostgreSQL database")
-
     async def query(
         self,
         sql: str,
@@ -164,17 +171,6 @@ class PostgreSQLDB:
             logger.error(f"PostgreSQL database,\nsql:{sql},\ndata:{data},\nerror:{e}")
             raise
 
-    @staticmethod
-    async def _prerequisite(conn: asyncpg.Connection, graph_name: str):
-        try:
-            await conn.execute('SET search_path = ag_catalog, "$user", public')  # type: ignore
-            await conn.execute(f"select create_graph('{graph_name}')")  # type: ignore
-        except (
-            asyncpg.exceptions.InvalidSchemaNameError,
-            asyncpg.exceptions.UniqueViolationError,
-        ):
-            pass
-
 
 class ClientManager:
     _instances: dict[str, Any] = {"db": None, "ref_count": 0}
@@ -554,24 +550,7 @@ class PGDocStatusStorage(DocStatusStorage):
 
     async def get_by_ids(self, ids: list[str]) -> list[dict[str, Any]]:
         """Get doc_chunks data by id"""
-        sql = SQL_TEMPLATES["get_by_ids_" + self.namespace].format(
-            ids=",".join([f"'{id}'" for id in ids])
-        )
-        params = {"workspace": self.db.workspace}
-        if is_namespace(self.namespace, NameSpace.KV_STORE_LLM_RESPONSE_CACHE):
-            array_res = await self.db.query(sql, params, multirows=True)
-            modes = set()
-            dict_res: dict[str, dict] = {}
-            for row in array_res:
-                modes.add(row["mode"])
-            for mode in modes:
-                if mode not in dict_res:
-                    dict_res[mode] = {}
-            for row in array_res:
-                dict_res[row["mode"]][row["id"]] = row
-            return [{k: v} for k, v in dict_res.items()]
-        else:
-            return await self.db.query(sql, params, multirows=True)
+        raise NotImplementedError
 
     async def get_status_counts(self) -> dict[str, int]:
         """Get counts of documents in each status"""
@@ -677,6 +656,8 @@ class PGGraphStorage(BaseGraphStorage):
     async def initialize(self):
         if self.db is None:
             self.db = await ClientManager.get_client()
+            # `check_graph_requirement` is required to be executed after `get_client`
+            # to ensure the graph is created before any query is executed.
             await self.db.check_graph_requirement(self.graph_name)
 
     async def finalize(self):