diff --git a/veadk/database/database_adapter.py b/veadk/database/database_adapter.py
index 28554787..0c0a5f19 100644
--- a/veadk/database/database_adapter.py
+++ b/veadk/database/database_adapter.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
 import re
 import time
 from typing import BinaryIO, TextIO
diff --git a/veadk/database/vector/opensearch_vector_database.py b/veadk/database/vector/opensearch_vector_database.py
index e6a7763f..9cdf7290 100644
--- a/veadk/database/vector/opensearch_vector_database.py
+++ b/veadk/database/vector/opensearch_vector_database.py
@@ -186,7 +186,7 @@ def query(self, query: str, **kwargs: Any) -> list[str]:
         assert collection_name is not None, "Collection name is required."
         if not self._opensearch_client.indices.exists(index=collection_name):
             logger.warning(
-                f"querying {query}, but collection {collection_name} does not exist. retun a empty list."
+                f"querying {query}, but collection {collection_name} does not exist. return a empty list."
             )
             return []
         query_vector = self._embedding_client.embed_query(query)
@@ -196,10 +196,58 @@ def query(self, query: str, **kwargs: Any) -> list[str]:
 
     @override
     def delete(self, collection_name: str, **kwargs: Any):
+        """drop index"""
         if not self._opensearch_client.indices.exists(index=collection_name):
             raise ValueError(f"Collection {collection_name} does not exist.")
         self._opensearch_client.indices.delete(index=collection_name)
 
-    def is_empty(self, collection_name: str):
+    def is_empty(self, collection_name: str) -> bool:
         response = self._opensearch_client.count(index=collection_name)
         return response["count"] == 0
+
+    def collection_exists(self, collection_name: str) -> bool:
+        return self._opensearch_client.indices.exists(index=collection_name)
+
+    def list_all_collection(self) -> list:
+        """List all index name of OpenSearch."""
+        response = self._opensearch_client.indices.get_alias()
+        return list(response.keys())
+
+    def get_all_docs(self, collection_name: str, size: int = 10000) -> list[dict]:
+        """Match all docs in one index of OpenSearch"""
+        if not self.collection_exists(collection_name):
+            logger.warning(
+                f"Get all docs, but collection {collection_name} does not exist. return a empty list."
+            )
+            return []
+
+        query = {"size": size, "query": {"match_all": {}}}
+        response = self._opensearch_client.search(index=collection_name, body=query)
+        return [
+            {
+                "id": hit["_id"],
+                "page_content": hit["_source"]["page_content"],
+            }
+            for hit in response["hits"]["hits"]
+        ]
+
+    def delete_by_query(self, collection_name: str, query: str):
+        """Delete docs by query in one index of OpenSearch"""
+        if not self.collection_exists(collection_name):
+            raise ValueError(f"Collection {collection_name} does not exist.")
+
+        query = {"query": {"match": {"page_content": query}}}
+        response = self._opensearch_client.delete_by_query(
+            index=collection_name, body=query
+        )
+        self._opensearch_client.indices.refresh(index=collection_name)
+        return response
+
+    def delete_by_id(self, collection_name: str, id: str):
+        """Delete docs by id in index of OpenSearch"""
+        if not self.collection_exists(collection_name):
+            raise ValueError(f"Collection {collection_name} does not exist.")
+
+        response = self._opensearch_client.delete(index=collection_name, id=id)
+        self._opensearch_client.indices.refresh(index=collection_name)
+        return response
diff --git a/veadk/memory/long_term_memory.py b/veadk/memory/long_term_memory.py
index 1a5ae0a9..acf5669c 100644
--- a/veadk/memory/long_term_memory.py
+++ b/veadk/memory/long_term_memory.py
@@ -81,7 +81,7 @@ def _filter_and_convert_events(self, events: list[Event]) -> list[str]:
             # convert: to string-format for storage
             message = event.content.model_dump(exclude_none=True, mode="json")
 
-            final_events.append(json.dumps(message))
+            final_events.append(json.dumps(message, ensure_ascii=False))
         return final_events
 
     @override