Fix backwards compatibility with upcoming threads schema changes. (#14045)

Ensure that the upsert will work properly by first updating any existing
rows (in the same way that the background update to backfill data works).

changelog.d/14045.misc

+Ensure Synapse v1.69 works with upcoming database changes in v1.70.

synapse/storage/databases/main/event_push_actions.py

@@ -1103,19 +1103,26 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
                 txn, room_id, user_id, stream_ordering, old_rotate_stream_ordering
             )
 
+            # First ensure that the existing rows have an updated thread_id field.
+            self.db_pool.simple_update_txn(
+                txn,
+                table="event_push_summary",
+                keyvalues={"room_id": room_id, "user_id": user_id, "thread_id": None},
+                updatevalues={"thread_id": "main"},
+            )
+
             # Replace the previous summary with the new counts.
             #
             # TODO(threads): Upsert per-thread instead of setting them all to main.
             self.db_pool.simple_upsert_txn(
                 txn,
                 table="event_push_summary",
-                keyvalues={"room_id": room_id, "user_id": user_id},
+                keyvalues={"room_id": room_id, "user_id": user_id, "thread_id": "main"},
                 values={
                     "notif_count": notif_count,
                     "unread_count": unread_count,
                     "stream_ordering": old_rotate_stream_ordering,
                     "last_receipt_stream_ordering": stream_ordering,
-                    "thread_id": "main",
                 },
             )
 
@@ -1264,20 +1271,25 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
 
         logger.info("Rotating notifications, handling %d rows", len(summaries))
 
+        # Ensure that any updated threads have an updated thread_id.
+        self.db_pool.simple_update_many_txn(
+            txn,
+            table="event_push_summary",
+            key_names=("user_id", "room_id", "thread_id"),
+            key_values=[(user_id, room_id, None) for user_id, room_id in summaries],
+            value_names=("thread_id",),
+            value_values=[("main",) for _ in summaries],
+        )
+
         # TODO(threads): Update on a per-thread basis.
         self.db_pool.simple_upsert_many_txn(
             txn,
             table="event_push_summary",
-            key_names=("user_id", "room_id"),
-            key_values=[(user_id, room_id) for user_id, room_id in summaries],
-            value_names=("notif_count", "unread_count", "stream_ordering", "thread_id"),
+            key_names=("user_id", "room_id", "thread_id"),
+            key_values=[(user_id, room_id, "main") for user_id, room_id in summaries],
+            value_names=("notif_count", "unread_count", "stream_ordering"),
             value_values=[
-                (
-                    summary.notif_count,
-                    summary.unread_count,
-                    summary.stream_ordering,
-                    "main",
-                )
+                (summary.notif_count, summary.unread_count, summary.stream_ordering)
                 for summary in summaries.values()
             ],
         )