Fix non-strings in the event_search table (#12037)

Don't attempt to add non-string `value`s to `event_search` and add a
background update to clear out bad rows from `event_search` when
using sqlite.

Signed-off-by: Sean Quah <seanq@element.io>

tests/storage/test_room_search.py

@@ -13,13 +13,16 @@
 # limitations under the License.
 
 import synapse.rest.admin
+from synapse.api.constants import EventTypes
+from synapse.api.errors import StoreError
 from synapse.rest.client import login, room
 from synapse.storage.engines import PostgresEngine
 
-from tests.unittest import HomeserverTestCase
+from tests.unittest import HomeserverTestCase, skip_unless
+from tests.utils import USE_POSTGRES_FOR_TESTS
 
 
-class NullByteInsertionTest(HomeserverTestCase):
+class EventSearchInsertionTest(HomeserverTestCase):
     servlets = [
         synapse.rest.admin.register_servlets_for_client_rest_resource,
         login.register_servlets,
@@ -72,3 +75,113 @@ class NullByteInsertionTest(HomeserverTestCase):
         )
         if isinstance(store.database_engine, PostgresEngine):
             self.assertIn("alice", result.get("highlights"))
+
+    def test_non_string(self):
+        """Test that non-string `value`s are not inserted into `event_search`.
+
+        This is particularly important when using sqlite, since a sqlite column can hold
+        both strings and integers. When using Postgres, integers are automatically
+        converted to strings.
+
+        Regression test for #11918.
+        """
+        store = self.hs.get_datastores().main
+
+        # Register a user and create a room
+        user_id = self.register_user("alice", "password")
+        access_token = self.login("alice", "password")
+        room_id = self.helper.create_room_as("alice", tok=access_token)
+        room_version = self.get_success(store.get_room_version(room_id))
+
+        # Construct a message with a numeric body to be received over federation
+        # The message can't be sent using the client API, since Synapse's event
+        # validation will reject it.
+        prev_event_ids = self.get_success(store.get_prev_events_for_room(room_id))
+        prev_event = self.get_success(store.get_event(prev_event_ids[0]))
+        prev_state_map = self.get_success(
+            self.hs.get_storage().state.get_state_ids_for_event(prev_event_ids[0])
+        )
+
+        event_dict = {
+            "type": EventTypes.Message,
+            "content": {"msgtype": "m.text", "body": 2},
+            "room_id": room_id,
+            "sender": user_id,
+            "depth": prev_event.depth + 1,
+            "prev_events": prev_event_ids,
+            "origin_server_ts": self.clock.time_msec(),
+        }
+        builder = self.hs.get_event_builder_factory().for_room_version(
+            room_version, event_dict
+        )
+        event = self.get_success(
+            builder.build(
+                prev_event_ids=prev_event_ids,
+                auth_event_ids=self.hs.get_event_auth_handler().compute_auth_events(
+                    builder,
+                    prev_state_map,
+                    for_verification=False,
+                ),
+                depth=event_dict["depth"],
+            )
+        )
+
+        # Receive the event
+        self.get_success(
+            self.hs.get_federation_event_handler().on_receive_pdu(
+                self.hs.hostname, event
+            )
+        )
+
+        # The event should not have an entry in the `event_search` table
+        f = self.get_failure(
+            store.db_pool.simple_select_one_onecol(
+                "event_search",
+                {"room_id": room_id, "event_id": event.event_id},
+                "event_id",
+            ),
+            StoreError,
+        )
+        self.assertEqual(f.value.code, 404)
+
+    @skip_unless(not USE_POSTGRES_FOR_TESTS, "requires sqlite")
+    def test_sqlite_non_string_deletion_background_update(self):
+        """Test the background update to delete bad rows from `event_search`."""
+        store = self.hs.get_datastores().main
+
+        # Populate `event_search` with dummy data
+        self.get_success(
+            store.db_pool.simple_insert_many(
+                "event_search",
+                keys=["event_id", "room_id", "key", "value"],
+                values=[
+                    ("event1", "room_id", "content.body", "hi"),
+                    ("event2", "room_id", "content.body", "2"),
+                    ("event3", "room_id", "content.body", 3),
+                ],
+                desc="populate_event_search",
+            )
+        )
+
+        # Run the background update
+        store.db_pool.updates._all_done = False
+        self.get_success(
+            store.db_pool.simple_insert(
+                "background_updates",
+                {
+                    "update_name": "event_search_sqlite_delete_non_strings",
+                    "progress_json": "{}",
+                },
+            )
+        )
+        self.wait_for_background_updates()
+
+        # The non-string `value`s ought to be gone now.
+        values = self.get_success(
+            store.db_pool.simple_select_onecol(
+                "event_search",
+                {"room_id": "room_id"},
+                "value",
+            ),
+        )
+        self.assertCountEqual(values, ["hi", "2"])