diff --git a/lightrag/kg/postgres_impl.py b/lightrag/kg/postgres_impl.py
index 3816b360..13f7d5d1 100644
--- a/lightrag/kg/postgres_impl.py
+++ b/lightrag/kg/postgres_impl.py
@@ -438,16 +438,26 @@ class PGVectorStorage(BaseVectorStorage):
 @dataclass
 class PGDocStatusStorage(DocStatusStorage):
     async def filter_keys(self, keys: set[str]) -> set[str]:
-        """Return keys that don't exist in storage"""
-        keys = ",".join([f"'{_id}'" for _id in keys])
-        sql = f"SELECT id FROM LIGHTRAG_DOC_STATUS WHERE workspace='{self.db.workspace}' AND id IN ({keys})"
-        result = await self.db.query(sql, multirows=True)
-        # The result is like [{'id': 'id1'}, {'id': 'id2'}, ...].
-        if result is None:
-            return set(keys)
-        else:
-            existed = set([element["id"] for element in result])
-            return set(keys) - existed
+        """Filter out duplicated content"""
+        sql = SQL_TEMPLATES["filter_keys"].format(
+            table_name=namespace_to_table_name(self.namespace),
+            ids=",".join([f"'{id}'" for id in keys]),
+        )
+        params = {"workspace": self.db.workspace}
+        try:
+            res = await self.db.query(sql, params, multirows=True)
+            if res:
+                exist_keys = [key["id"] for key in res]
+            else:
+                exist_keys = []
+            new_keys = set([s for s in keys if s not in exist_keys])
+            print(f"keys: {keys}")
+            print(f"new_keys: {new_keys}")
+            return new_keys
+        except Exception as e:
+            logger.error(f"PostgreSQL database error: {e}")
+            print(sql)
+            print(params)
 
     async def get_by_id(self, id: str) -> Union[dict[str, Any], None]:
         sql = "select * from LIGHTRAG_DOC_STATUS where workspace=$1 and id=$2"