try to load members from database first and cache them in-memory

lib/src/database/database.dart

@@ -528,6 +528,15 @@ class Database extends _$Database {
     return sdk.Event.fromDb(res.first, room).asUser;
   }
 
+  Future<List<sdk.User>> getUsers(int clientId, sdk.Room room) async {
+    final res = await dbGetUsers(clientId, room.id).get();
+    final ret = <sdk.User>[];
+    for (final r in res) {
+      ret.add(sdk.Event.fromDb(r, room).asUser);
+    }
+    return ret;
+  }
+
   Future<List<sdk.Event>> getEventList(int clientId, sdk.Room room) async {
     final res = await dbGetEventList(clientId, room.id).get();
     final eventList = <sdk.Event>[];

lib/src/database/database.g.dart

@@ -6196,21 +6196,11 @@ abstract class _$Database extends GeneratedDatabase {
         }).map(_rowToDbRoomState);
   }
 
-  Selectable<DbRoomState> dbGetUsers(
-      int client_id, List<String> mxids, String room_id) {
-    var $arrayStartIndex = 2;
-    final expandedmxids = $expandVar($arrayStartIndex, mxids.length);
-    $arrayStartIndex += mxids.length;
+  Selectable<DbRoomState> dbGetUsers(int client_id, String room_id) {
     return customSelect(
-        'SELECT * FROM room_states WHERE client_id = :client_id AND type = \'m.room.member\' AND state_key IN ($expandedmxids) AND room_id = :room_id',
-        variables: [
-          Variable.withInt(client_id),
-          for (var $ in mxids) Variable.withString($),
-          Variable.withString(room_id)
-        ],
-        readsFrom: {
-          roomStates
-        }).map(_rowToDbRoomState);
+        'SELECT * FROM room_states WHERE client_id = :client_id AND type = \'m.room.member\' AND room_id = :room_id',
+        variables: [Variable.withInt(client_id), Variable.withString(room_id)],
+        readsFrom: {roomStates}).map(_rowToDbRoomState);
   }
 
   DbEvent _rowToDbEvent(QueryRow row) {

lib/src/database/database.moor

@@ -216,6 +216,7 @@ storeRoomState: INSERT OR REPLACE INTO room_states (client_id, event_id, room_id
 getAllRoomAccountData: SELECT * FROM room_account_data WHERE client_id = :client_id;
 storeRoomAccountData: INSERT OR REPLACE INTO room_account_data (client_id, type, room_id, content) VALUES (:client_id, :type, :room_id, :content);
 dbGetUser: SELECT * FROM room_states WHERE client_id = :client_id AND type = 'm.room.member' AND state_key = :state_key AND room_id = :room_id;
+dbGetUsers: SELECT * FROM room_states WHERE client_id = :client_id AND type = 'm.room.member' AND room_id = :room_id;
 dbGetEventList: SELECT * FROM events WHERE client_id = :client_id AND room_id = :room_id GROUP BY event_id ORDER BY sort_order DESC;
 getStates: SELECT * FROM room_states WHERE client_id = :client_id AND room_id = :room_id;
 resetNotificationCount: UPDATE rooms SET notification_count = 0, highlight_count = 0 WHERE client_id = :client_id AND room_id = :room_id;

lib/src/room.dart

@@ -1004,10 +1004,20 @@ class Room {
   /// Request the full list of participants from the server. The local list
   /// from the store is not complete if the client uses lazy loading.
   Future<List<User>> requestParticipants() async {
+    if (!participantListComplete && partial && client.database != null) {
+      // we aren't fully loaded, maybe the users are in the database
+      final users = await client.database.getUsers(client.id, this);
+      for (final user in users) {
+        setState(user);
+      }
+    }
     if (participantListComplete) return getParticipants();
     final matrixEvents = await client.api.requestMembers(id);
     final users =
         matrixEvents.map((e) => Event.fromMatrixEvent(e, this).asUser).toList();
+    for (final user in users) {
+      setState(user); // at *least* cache this in-memory
+    }
     users.removeWhere(
         (u) => [Membership.leave, Membership.ban].contains(u.membership));
     return users;