feat: Support returning all sessions when user_id is none in the request

resolves https://github.com/google/adk-python/issues/3154

PiperOrigin-RevId: 819417330

src/google/adk/sessions/base_session_service.py

@@ -83,18 +83,9 @@ class BaseSessionService(abc.ABC):
 
   @abc.abstractmethod
   async def list_sessions(
-      self, *, app_name: str, user_id: Optional[str] = None
+      self, *, app_name: str, user_id: str
   ) -> ListSessionsResponse:
-    """Lists all the sessions for a user.
-
-    Args:
-      app_name: The name of the app.
-      user_id: The ID of the user. If not provided, lists all sessions for all
-        users.
-
-    Returns:
-      A ListSessionsResponse containing the sessions.
-    """
+    """Lists all the sessions."""
 
   @abc.abstractmethod
   async def delete_session(

src/google/adk/sessions/database_session_service.py

@@ -554,42 +554,30 @@ class DatabaseSessionService(BaseSessionService):
 
   @override
   async def list_sessions(
-      self, *, app_name: str, user_id: Optional[str] = None
+      self, *, app_name: str, user_id: str
   ) -> ListSessionsResponse:
     with self.database_session_factory() as sql_session:
-      query = sql_session.query(StorageSession).filter(
-          StorageSession.app_name == app_name
+      results = (
+          sql_session.query(StorageSession)
+          .filter(StorageSession.app_name == app_name)
+          .filter(StorageSession.user_id == user_id)
+          .all()
       )
-      if user_id is not None:
-        query = query.filter(StorageSession.user_id == user_id)
-      results = query.all()
 
-      # Fetch app state from storage
+      # Fetch states from storage
       storage_app_state = sql_session.get(StorageAppState, (app_name))
-      app_state = storage_app_state.state if storage_app_state else {}
+      storage_user_state = sql_session.get(
+          StorageUserState, (app_name, user_id)
+      )
 
-      # Fetch user state(s) from storage
-      user_states_map = {}
-      if user_id is not None:
-        storage_user_state = sql_session.get(
-            StorageUserState, (app_name, user_id)
-        )
-        if storage_user_state:
-          user_states_map[user_id] = storage_user_state.state
-      else:
-        all_user_states_for_app = (
-            sql_session.query(StorageUserState)
-            .filter(StorageUserState.app_name == app_name)
-            .all()
-        )
-        for storage_user_state in all_user_states_for_app:
-          user_states_map[storage_user_state.user_id] = storage_user_state.state
+      app_state = storage_app_state.state if storage_app_state else {}
+      user_state = storage_user_state.state if storage_user_state else {}
 
       sessions = []
       for storage_session in results:
         session_state = storage_session.state
-        user_state = user_states_map.get(storage_session.user_id, {})
         merged_state = _merge_state(app_state, user_state, session_state)
+
         sessions.append(storage_session.to_session(state=merged_state))
       return ListSessionsResponse(sessions=sessions)
 

src/google/adk/sessions/in_memory_session_service.py

@@ -201,41 +201,31 @@ class InMemorySessionService(BaseSessionService):
 
   @override
   async def list_sessions(
-      self, *, app_name: str, user_id: Optional[str] = None
+      self, *, app_name: str, user_id: str
   ) -> ListSessionsResponse:
     return self._list_sessions_impl(app_name=app_name, user_id=user_id)
 
   def list_sessions_sync(
-      self, *, app_name: str, user_id: Optional[str] = None
+      self, *, app_name: str, user_id: str
   ) -> ListSessionsResponse:
     logger.warning('Deprecated. Please migrate to the async method.')
     return self._list_sessions_impl(app_name=app_name, user_id=user_id)
 
   def _list_sessions_impl(
-      self, *, app_name: str, user_id: Optional[str] = None
+      self, *, app_name: str, user_id: str
   ) -> ListSessionsResponse:
     empty_response = ListSessionsResponse()
     if app_name not in self.sessions:
       return empty_response
-    if user_id is not None and user_id not in self.sessions[app_name]:
+    if user_id not in self.sessions[app_name]:
       return empty_response
 
     sessions_without_events = []
-
-    if user_id is None:
-      for user_id in self.sessions[app_name]:
-        for session_id in self.sessions[app_name][user_id]:
-          session = self.sessions[app_name][user_id][session_id]
-          copied_session = copy.deepcopy(session)
-          copied_session.events = []
-          copied_session = self._merge_state(app_name, user_id, copied_session)
-          sessions_without_events.append(copied_session)
-    else:
-      for session in self.sessions[app_name][user_id].values():
-        copied_session = copy.deepcopy(session)
-        copied_session.events = []
-        copied_session = self._merge_state(app_name, user_id, copied_session)
-        sessions_without_events.append(copied_session)
+    for session in self.sessions[app_name][user_id].values():
+      copied_session = copy.deepcopy(session)
+      copied_session.events = []
+      copied_session = self._merge_state(app_name, user_id, copied_session)
+      sessions_without_events.append(copied_session)
     return ListSessionsResponse(sessions=sessions_without_events)
 
   @override

src/google/adk/sessions/vertex_ai_session_service.py

@@ -200,25 +200,22 @@ class VertexAiSessionService(BaseSessionService):
 
   @override
   async def list_sessions(
-      self, *, app_name: str, user_id: Optional[str] = None
+      self, *, app_name: str, user_id: str
   ) -> ListSessionsResponse:
     reasoning_engine_id = self._get_reasoning_engine_id(app_name)
     api_client = self._get_api_client()
 
     sessions = []
-    config = {}
-    if user_id is not None:
-      config['filter'] = f'user_id="{user_id}"'
     sessions_iterator = api_client.agent_engines.sessions.list(
         name=f'reasoningEngines/{reasoning_engine_id}',
-        config=config,
+        config={'filter': f'user_id="{user_id}"'},
     )
 
     for api_session in sessions_iterator:
       sessions.append(
           Session(
               app_name=app_name,
-              user_id=api_session.user_id,
+              user_id=user_id,
               id=api_session.name.split('/')[-1],
               state=getattr(api_session, 'session_state', None) or {},
               last_update_time=api_session.update_time.timestamp(),