Remove option to skip locking of tables during emulated upserts (#14469)

To perform an emulated upsert into a table safely, we must either:
 * lock the table,
 * be the only writer upserting into the table
 * or rely on another unique index being present.

When the 2nd or 3rd cases were applicable, we previously avoided locking
the table as an optimization. However, as seen in #14406, it is easy to
slip up when adding new schema deltas and corrupt the database.

The only time we lock when performing emulated upserts is while waiting
for background updates on postgres. On sqlite, we do no locking at all.

Let's remove the option to skip locking tables, so that we don't shoot
ourselves in the foot again.

Signed-off-by: Sean Quah <seanq@matrix.org>

8 files changed, 0 insertions, 36 deletions

diff --git a/synapse/storage/databases/main/account_data.py b/synapse/storage/databases/main/account_data.py
index 282687ebce..07908c41d9 100644
--- a/synapse/storage/databases/main/account_data.py
+++ b/synapse/storage/databases/main/account_data.py
@@ -449,9 +449,6 @@ class AccountDataWorkerStore(PushRulesWorkerStore, CacheInvalidationWorkerStore)
         content_json = json_encoder.encode(content)
 
         async with self._account_data_id_gen.get_next() as next_id:
-            # no need to lock here as room_account_data has a unique constraint
-            # on (user_id, room_id, account_data_type) so simple_upsert will
-            # retry if there is a conflict.
             await self.db_pool.simple_upsert(
                 desc="add_room_account_data",
                 table="room_account_data",
@@ -461,7 +458,6 @@ class AccountDataWorkerStore(PushRulesWorkerStore, CacheInvalidationWorkerStore)
                     "account_data_type": account_data_type,
                 },
                 values={"stream_id": next_id, "content": content_json},
-                lock=False,
             )
 
             self._account_data_stream_cache.entity_has_changed(user_id, next_id)
@@ -517,15 +513,11 @@ class AccountDataWorkerStore(PushRulesWorkerStore, CacheInvalidationWorkerStore)
     ) -> None:
         content_json = json_encoder.encode(content)
 
-        # no need to lock here as account_data has a unique constraint on
-        # (user_id, account_data_type) so simple_upsert will retry if
-        # there is a conflict.
         self.db_pool.simple_upsert_txn(
             txn,
             table="account_data",
             keyvalues={"user_id": user_id, "account_data_type": account_data_type},
             values={"stream_id": next_id, "content": content_json},
-            lock=False,
         )
 
         # Ignored users get denormalized into a separate table as an optimisation.
diff --git a/synapse/storage/databases/main/appservice.py b/synapse/storage/databases/main/appservice.py
index 63046c0527..25da0c56c5 100644
--- a/synapse/storage/databases/main/appservice.py
+++ b/synapse/storage/databases/main/appservice.py
@@ -451,8 +451,6 @@ class ApplicationServiceTransactionWorkerStore(
             table="application_services_state",
             keyvalues={"as_id": service.id},
             values={f"{stream_type}_stream_id": pos},
-            # no need to lock when emulating upsert: as_id is a unique key
-            lock=False,
             desc="set_appservice_stream_type_pos",
         )
 
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index 05a193f889..534f7fc04a 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -1744,9 +1744,6 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
                 table="device_lists_remote_cache",
                 keyvalues={"user_id": user_id, "device_id": device_id},
                 values={"content": json_encoder.encode(content)},
-                # we don't need to lock, because we assume we are the only thread
-                # updating this user's devices.
-                lock=False,
             )
 
         txn.call_after(self._get_cached_user_device.invalidate, (user_id, device_id))
@@ -1760,9 +1757,6 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
             table="device_lists_remote_extremeties",
             keyvalues={"user_id": user_id},
             values={"stream_id": stream_id},
-            # again, we can assume we are the only thread updating this user's
-            # extremity.
-            lock=False,
         )
 
     async def update_remote_device_list_cache(
@@ -1815,9 +1809,6 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
             table="device_lists_remote_extremeties",
             keyvalues={"user_id": user_id},
             values={"stream_id": stream_id},
-            # we don't need to lock, because we can assume we are the only thread
-            # updating this user's extremity.
-            lock=False,
         )
 
     async def add_device_change_to_streams(
diff --git a/synapse/storage/databases/main/event_federation.py b/synapse/storage/databases/main/event_federation.py
index 309a4ba664..bbee02ab18 100644
--- a/synapse/storage/databases/main/event_federation.py
+++ b/synapse/storage/databases/main/event_federation.py
@@ -1686,7 +1686,6 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas
             },
             insertion_values={},
             desc="insert_insertion_extremity",
-            lock=False,
         )
 
     async def insert_received_event_to_staging(
diff --git a/synapse/storage/databases/main/pusher.py b/synapse/storage/databases/main/pusher.py
index fee37b9ce4..40fd781a6a 100644
--- a/synapse/storage/databases/main/pusher.py
+++ b/synapse/storage/databases/main/pusher.py
@@ -325,14 +325,11 @@ class PusherWorkerStore(SQLBaseStore):
     async def set_throttle_params(
         self, pusher_id: str, room_id: str, params: ThrottleParams
     ) -> None:
-        # no need to lock because `pusher_throttle` has a primary key on
-        # (pusher, room_id) so simple_upsert will retry
         await self.db_pool.simple_upsert(
             "pusher_throttle",
             {"pusher": pusher_id, "room_id": room_id},
             {"last_sent_ts": params.last_sent_ts, "throttle_ms": params.throttle_ms},
             desc="set_throttle_params",
-            lock=False,
         )
 
     async def _remove_deactivated_pushers(self, progress: dict, batch_size: int) -> int:
@@ -589,8 +586,6 @@ class PusherStore(PusherWorkerStore, PusherBackgroundUpdatesStore):
         device_id: Optional[str] = None,
     ) -> None:
         async with self._pushers_id_gen.get_next() as stream_id:
-            # no need to lock because `pushers` has a unique key on
-            # (app_id, pushkey, user_name) so simple_upsert will retry
             await self.db_pool.simple_upsert(
                 table="pushers",
                 keyvalues={"app_id": app_id, "pushkey": pushkey, "user_name": user_id},
@@ -609,7 +604,6 @@ class PusherStore(PusherWorkerStore, PusherBackgroundUpdatesStore):
                     "device_id": device_id,
                 },
                 desc="add_pusher",
-                lock=False,
             )
 
             user_has_pusher = self.get_if_user_has_pusher.cache.get_immediate(
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index 52ad947c6c..1309bfd374 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -1847,9 +1847,6 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
                 "creator": room_creator,
                 "has_auth_chain_index": has_auth_chain_index,
             },
-            # rooms has a unique constraint on room_id, so no need to lock when doing an
-            # emulated upsert.
-            lock=False,
         )
 
     async def store_partial_state_room(
@@ -1970,9 +1967,6 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
                 "creator": "",
                 "has_auth_chain_index": has_auth_chain_index,
             },
-            # rooms has a unique constraint on room_id, so no need to lock when doing an
-            # emulated upsert.
-            lock=False,
         )
 
     async def set_room_is_public(self, room_id: str, is_public: bool) -> None:
diff --git a/synapse/storage/databases/main/room_batch.py b/synapse/storage/databases/main/room_batch.py
index 39e80f6f5b..131f357d04 100644
--- a/synapse/storage/databases/main/room_batch.py
+++ b/synapse/storage/databases/main/room_batch.py
@@ -44,6 +44,4 @@ class RoomBatchStore(SQLBaseStore):
             table="event_to_state_groups",
             keyvalues={"event_id": event_id},
             values={"state_group": state_group_id, "event_id": event_id},
-            # Unique constraint on event_id so we don't have to lock
-            lock=False,
         )
diff --git a/synapse/storage/databases/main/user_directory.py b/synapse/storage/databases/main/user_directory.py
index 698d6f7515..044435deab 100644
--- a/synapse/storage/databases/main/user_directory.py
+++ b/synapse/storage/databases/main/user_directory.py
@@ -481,7 +481,6 @@ class UserDirectoryBackgroundUpdateStore(StateDeltasStore):
                 table="user_directory",
                 keyvalues={"user_id": user_id},
                 values={"display_name": display_name, "avatar_url": avatar_url},
-                lock=False,  # We're only inserter
             )
 
             if isinstance(self.database_engine, PostgresEngine):
@@ -511,7 +510,6 @@ class UserDirectoryBackgroundUpdateStore(StateDeltasStore):
                     table="user_directory_search",
                     keyvalues={"user_id": user_id},
                     values={"value": value},
-                    lock=False,  # We're only inserter
                 )
             else:
                 # This should be unreachable.