Add column to track where we partial-joined via

Author: David Robertson

synapse/storage/schema/main/delta/73/09partial_joined_via_destination.sql

@@ -0,0 +1,19 @@
+/* Copyright 2022 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * 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.
+ */
+
+-- When we resync partial state, we prioritise doing so using the server we
+-- partial-joined from. To do this we need to record which server that was!
+-- Both columns are backwards compatible.
+ALTER TABLE partial_state_rooms ADD COLUMN joined_via TEXT;